Database Develop

TWRP can't decrypt /data on CM12.1

I just decided to move to CM12.1 on my Droid Turbo (XT1254) after the 1/27 Snapshot (YOG7DAO3J1) was posted. I am running this with TWRP 2.8.7.0, BHB27 Kernel, and OpenGAPPS 5.1. So far, almost everything has been fantastic and the performance of the device is like night and day compared to the Verizon software.
My problem is that the CM12.1 ROM has my device encrypted to begin with, which is nice but giving me trouble. I can't get into TWRP to install Xposed framework or other .zips via ADB. I have tried the following:
Disabling require password on startup
Changing the password in Android
Changing the password from root ADB shell
Using a pin
Trying "default_password"
Can anyone give me a solution or some advice? Any help is greatly appreciated!

Having same issue with TWRP not recognizing any decryption password given... Any ideas out there? Is TWRP incompatible with Droid Turbo HW Encryption, or ?

P_6 said:
Having same issue with TWRP not recognizing any decryption password given... Any ideas out there? Is TWRP incompatible with Droid Turbo HW Encryption, or ?
Click to expand...
Click to collapse
This thread is kinda old and I assumed nobody really knew what was going on with it either. I ended up just not using the encryption. The first time around mine was encrypted without me knowing, which was the issue. I just wiped all partitions and flashed the ROM again...

I am having a similar issue so i thought i would chime in, despite the older thread. I had a stock ROM that was encrypted and I was able to unlock and root with SunShine fine. Flashed on TWRP 2.8.7 and ran into a "Unable to mount storage. Failed to decrypt data" error. Updated to TWRP 3.0.0 and still have the same issue. Still working through a resolution as the phone is still functional if I just boot normally. When you mentioned you wiped all partitions, what process did you use? If i can just get access to the interal storage I can flash a ROM and be good to go.

Asyt said:
I am having a similar issue so i thought i would chime in, despite the older thread. I had a stock ROM that was encrypted and I was able to unlock and root with SunShine fine. Flashed on TWRP 2.8.7 and ran into a "Unable to mount storage. Failed to decrypt data" error. Updated to TWRP 3.0.0 and still have the same issue. Still working through a resolution as the phone is still functional if I just boot normally. When you mentioned you wiped all partitions, what process did you use? If i can just get access to the interal storage I can flash a ROM and be good to go.
Click to expand...
Click to collapse
So far, the only way I have been able to get encryption working with CM12.1 on the Droid Turbo is to do the folllowing (Note: This assumes you have bootloader unlocked and TWRP installed as your recovery):
Part 0: Make sure you have what you need
1. Stock Droid Turbo Firmware SU4TL for your device
2. The version of CyanogenMod 12.1 that you need. I recommend a Snapshot, but it's up to you.
3. TWRP 3.0.0 or later for your Droid Turbo.
Part 1: Final set up (Yes, we do this first)
1. Download CM12.1 & Download OpenGapps arm for 5.1
2. Wipe device (system, data, cache, internal storage), copy CM12 install zip and opengapps install zip via USB to device.
3. Flash CM12 and OpenGapps in TWRP
4. Set up device how you want it to be (install your apps, set up your accounts, etc).
5. Set whatever lock-screen PIN / Password / Pattern you are going to want on your phone in general!
6. Make a Nandroid backup of your 100% set up phone in TWRP
7. Copy your backup TWRP folder to your PC.
Part 2: Encrypt device and put everything back how we want it.
1. Flash stock Verizon firmware (SU4TL) via Fastboot. Do not flash stock Recovery, but put back TWRP if you did somehow (I use a simple bash script I have attached below).
2. Boot device, go through initial set up, don't download apps (we're going to be wiping the device soon).
3. Make sure your battery is 80%+ charged, and your device is plugged in.
4. Set a password or PIN on your phone.
5. Encrypt your device (this will be fairly fast, as /data is empty, but you should be asked for your encryption password on boot.)
6. Reboot to recovery. TWRP will ask you for your password to decrypt. It should work with no problem.
7. Copy your backed-up TWRP folder with your CM12 install to your device via USB. The TWRP folder goes in the Internal Storage root directory.
8. Still in TWRP (Do not reboot), go to Restore, and select the backup you just copied over. This will replace the stock rom with your CM12 backup.
9. Your CM12 install will be restored, but your device will remain Encrypted.
10. Reboot into CM12. Win.
You will need to decrypt your device every boot with the password that you selected when you initially encrypted your device. Your lock-screen password CAN BE DIFFERENT. That is why I do it this way. I have a fairly long password to decrypt my device on boot-up, but a pattern as my lock screen. That way I can quickly get into my phone during daily use without having to constantly type in a fairly complicated password.

Recover data after unsuccessful force encryption

I am in trouble of loosing all my userdata after following the below process:
1. I was on stable 4.5.1 and not encrypted.
2. flashed blue_spark 8.52 recovery.
3. Reboot to recovery and full wiped (except user data).
4. Flashed OOS beta 18 and Magisk 14.3.
5. Rebooted and waited for 20 min but was still on rebooting process.
6. Force rebooted to recovery and alas!, twrp asking for decrypt password!!!
7. Reboot to system and message appears as 'Encryption Unseccessful'
I am not been able to access any partition including userdata from TWRP (as it's asking password), OOS also not booted as well.
Now I will be grateful if someone have any knowledge to skip TWRP password and provide access to userdata to recovery/copy data (photos/files etc) from the device before format userdata and start over again.

If your data was previously decrypted then disable encryption, format data, install a ROM that does not enforce encryption, then try looking on the Play Store for photo recovery apps.
Note that it will not be possible to recover data from the encrypted part of the device. If you left it running for 20 minutes, the chances are your data is almost entirely gone at this point.

Like stated above, your data is probably destroyed since you interrupted the encryption process.
Have you tried "default_password" as the password in TWRP?

Are there 2 copies of /system on the phone?

My phone (3T) has an unlocked bootloader, is encrypted, not rooted, and running stock OOS 5.0.
I flashed TWRP and discovered that stock OOS restores the stock recovery in boot.
I saw the Oreo dm-verity thread by xenet, had a look at the zip file, noticed that it just modified fstab to prevent force encrypt, so I flashed it to see what happens.
And nothing happens. After the system had booted, fstab is unchanged from the original stock copy.
So I'm wondering whether this file is also restored when booting up on stock.
I get aggressive and go back to TWRP and delete /system/etc and /system/bin and modify build.prop.
Surely now the phone won't boot!
Wrong! It boots up and everything is back to normal in /system.
I go back to TWRP and have a look at /system and it shows me one without the etc and bin folders and has the modified build.prop.
What's going on? How can I see one version of /system in TWRP but a different version (ie, stock) when the phone has booted?
By the way I've been an Android user for many years and have rooted and flashed custom ROMs on a variety of phones and I've never seen anything like what's happening on my 3T. I'm sure that dm-verity is somehow involved in this.

Happened to me on my earlier OOS 5.0 attempts...
But i suspected Magisk is involved in my case.
I downloaded Magisk Module "System Terminal Debloater,"
remove some apps like Duo, Chrome, and Google Play Movies.
Some restarts, they magically re-appear again on Apps Drawer...
Haven't touch them yet again after....

nicknacknuke said:
Happened to me on my earlier OOS 5.0 attempts...
But i suspected Magisk is involved in my case.
I downloaded Magisk Module "System Terminal Debloater,"
remove some apps like Duo, Chrome, and Google Play Movies.
Some restarts, they magically re-appear again on Apps Drawer...
Haven't touch them yet again after....
Click to expand...
Click to collapse
Thanks.
I should have mentioned that I'm also not rooted. So stock OOS 5.0.
Sent from my OnePlus 3T using XDA Labs

When you boot TWRP for the first time, it should ask you if you want to put the /system in read/write mode or if you want to leave it unchanged, did you choose the right option?

Jackhass said:
When you boot TWRP for the first time, it should ask you if you want to put the /system in read/write mode or if you want to leave it unchanged, did you choose the right option?
Click to expand...
Click to collapse
No, I don't get that message because my phone is encrypted with a password. So the first thing I see in TWRP is the request for the password and then I'm presented with the menus.
However, in the Mounted menu, system isn't mounted and I have the option of mounting it in read-only mode.
Sent from my OnePlus 3T using XDA Labs

BillGoss said:
No, I don't get that message because my phone is encrypted with a password. So the first thing I see in TWRP is the request for the password and then I'm presented with the menus.
However, in the Mounted menu, system isn't mounted and I have the option of mounting it in read-only mode.
Click to expand...
Click to collapse
After first time flashing TWRP a folder gets created on your internal storage, with a hidden file called .twrps, go delete it and reboot recovery to trigger the message "allowing system modifications" on TWRP's first boot...
It's not about encryption, it's just that TWRP remember the decision you made due to the file I pointed out...
Sent from my OnePlus 3T using XDA Labs

Sam Nakamura said:
After first time flashing TWRP a folder gets created on your internal storage, with a hidden file called .twrps, go delete it and reboot recovery to trigger the message "allowing system modifications" on TWRP's first boot...
It's not about encryption, it's just that TWRP remember the decision you made due to the file I pointed out...
Click to expand...
Click to collapse
Somehow the attachment strikes on previous post
Edit: still not working, check your TWRP Folder on storage to find the file
Sent from my OnePlus 3T using XDA Labs

Sam Nakamura said:
Somehow the attachment strikes on previous post
Edit: still not working, check your TWRP Folder on storage to find the file
Click to expand...
Click to collapse
Thanks, you are correct. I'd forgotten that that TWRP remembers. Deleting .twrps does bring up the RO prompt after decrypting storage.
Jackhass said:
When you boot TWRP for the first time, it should ask you if you want to put the /system in read/write mode or if you want to leave it unchanged, did you choose the right option?
Click to expand...
Click to collapse
I had allowed changes to the system otherwise I couldn't have made changes to it, which includes the ability to restore the system partition.
But I'm still unclear why if I make changes to the system partition and boot with the stock kernel, then after the boot none of the changes are present in the system partition, but if I boot back into TWRP then the changes are all there.

I recall someone in another OOS 5 thread saying that the stock kernal replaces TWRP with stock recovery if you don't flash root (magisk/superSU). Is it possible that the kernel re-flashes system on boot? Another possibility is that TWRP thinks it's making changes to system but it's not actually? Not quite sure, I've never heard of anything like this before either, just throwing other ideas out there.
I've never read anything about the OP3T or any oneplus phones for that matter having A/B system partitions like the pixels. *shrug*

@nhshah7, something's like what you suggest must be going on to account for what I'm seeing. I'm hoping that someone can confirm my observations and provide a definite answer.

@BillGoss
My thread has been updated relating to all your queries...
Thank you...
https://forum.xda-developers.com/oneplus-3t/how-to/disable-dm-verity-force-encryption-op3t-t3688748

Xennet said:
@BillGoss
My thread has been updated relating to all your queries...
Thank you...
https://forum.xda-developers.com/oneplus-3t/how-to/disable-dm-verity-force-encryption-op3t-t3688748
Click to expand...
Click to collapse
Actually it doesn't explain how TWRP can make changes to system yet the phone boots up on an unmodified system if using the stock kernel. And then, when you boot back into TWRP and look at system, the changes are still there.
Where does the unmodified system come from?
Where does the modified system live?
Why doesn't modifying system result in a failed boot due to dm-verity, while restoring a backup of system does result in a failed boot?
So many questions with no answers.

BillGoss said:
....So many questions with no answers.
Click to expand...
Click to collapse
Not sure if this is applicable in your case but the following possibilities may be worth considering for you:
1. Are you sure that the system image is actually getting modified? If the system partition is not mounted before flashing the zip and the zip being flashed does not mount the system partition in read / write, then no changes to system partitions will actually be written.
2. If dm-verity is enabled, then restoring system could result in an error as this is different from restoring a system-image (nandroid copy of the whole partition and not just the files in the system partition). DM-verity can be triggered if the files are all the same but the dm-verity signature computed by hashing the system partition has changed.
3. For boot partitions, strange behaviour can occur if remnants of the previous boot.img are still in the partition (...e.g. if the previous boot.img was of larger size and a new boot.img of a smaller is flashed, then there will be some bytes after the new boot.img that are from the previous boot.img). To verify this, format the boot partition from fastboot and see if you notice anything different with the new boot.img.
4. In Oreo / 8.0, dm-verity flags are stored in dtb (device tree blobs) inside the kernel and not in the fstab file. Only data encryption can be changed from the fstab file and dm-verity needs to be changed from changing the dtb (...Magisk beta v1456 and SuperSu 2.82 SR4 do this, I think).

rk2612 said:
Not sure if this is applicable in your case but the following possibilities may be worth considering for you:
1. Are you sure that the system image is actually getting modified? If the system partition is not mounted before flashing the zip and the zip being flashed does not mount the system partition in read / write, then no changes to system partitions will actually be written.
2. If dm-verity is enabled, then restoring system could result in an error as this is different from restoring a system-image (nandroid copy of the whole partition and not just the files in the system partition). DM-verity can be triggered if the files are all the same but the dm-verity signature computed by hashing the system partition has changed.
3. For boot partitions, strange behaviour can occur if remnants of the previous boot.img are still in the partition (...e.g. if the previous boot.img was of larger size and a new boot.img of a smaller is flashed, then there will be some bytes after the new boot.img that are from the previous boot.img). To verify this, format the boot partition from fastboot and see if you notice anything different with the new boot.img.
4. In Oreo / 8.0, dm-verity flags are stored in dtb (device tree blobs) inside the kernel and not in the fstab file. Only data encryption can be changed from the fstab file and dm-verity needs to be changed from changing the dtb (...Magisk beta v1456 and SuperSu 2.82 SR4 do this, I think).
Click to expand...
Click to collapse
I'll come back to 1.
2. That makes sense and accounts for why a restore of the system partition with the stock boot image causes me to get dumped back in fastboot mode. If I flash the stock system zip file then the system boots properly.
3. I've not had any issues with strange boot behaviour. I'm always starting with stock or flashing kernels that modify the stock boot image, like Blu Spark.
4. I gathered this from my reading of various threads. If I want to make changes to the system partition and get them to stick and not fail dm-verity then I have to flash a custom kernel. I've proven this in my testing. (A rooting solution would also work, but I've not done this).
Back to 1:
Here's what I've done:
Starting with pure stock image (flash OOS 5.0).
Boot into fastboot and flash TWRP.
Boot into recovery.
Mount system as rw. (In ro mode the next step fails)
Delete the bin, etc, and lib folders in system using the TWRP file manager. (Screenshot a)
Reboot system.
... First interesting fact ...
System boots ok, deleted folders are present in file manager. (Screenshot b)
Boot into fastboot and flash TWRP. (Booting with stock restores stock recovery)
Mount system.
... Second interesting fact ...
TWRP file manager shows that deleted folders are missing. (Screenshot c)
Flash custom kernel or patched boot image
Reboot system
... Third interesting fact ...
System fails to boot. Hangs on splash screen.
So TWRP made the changes (otherwise how could they be visible between reboots, including a replacement of recovery) and I only did them once.
Yet they don't actually take effect until I replace the stock boot image.
So, where are the changes hiding? What did TWRP actually change?
Screenshots (note that TWRP has the wrong timezone set so the time shown is wrong):

BillGoss said:
....
Back to 1:
Here's what I've done:
Starting with pure stock image (flash OOS 5.0).
Boot into fastboot and flash TWRP.
Boot into recovery.
Mount system as rw. (In ro mode the next step fails)
Delete the bin, etc, and lib folders in system using the TWRP file manager. (Screenshot a)
Reboot system.
... First interesting fact ...
System boots ok, deleted folders are present in file manager. (Screenshot b)
Boot into fastboot and flash TWRP. (Booting with stock restores stock recovery)
Mount system.
... Second interesting fact ...
TWRP file manager shows that deleted folders are missing. (Screenshot c)
Flash custom kernel or patched boot image
Reboot system
... Third interesting fact ...
System fails to boot. Hangs on splash screen.
So TWRP made the changes (otherwise how could they be visible between reboots, including a replacement of recovery) and I only did them once.
Yet they don't actually take effect until I replace the stock boot image.
So, where are the changes hiding? What did TWRP actually change?
Screenshots (note that TWRP has the wrong timezone set so the time shown is wrong):
Click to expand...
Click to collapse
Some more thoughts for you to consider:
1. Have you tried this with the official TWRP recovery version 3.2.0-0?
2. Is there anything inside the folders that you see using the file manager after a regular boot? Folders of same name may exist in the boot ramdisk and these are merged with system folders after boot.
3. Try wiping cache between reboots and see if that changes any of your observations.

rk2612 said:
Some more thoughts for you to consider:
1. Have you tried this with the official TWRP recovery version 3.2.0-0?
2. Is there anything inside the folders that you see using the file manager after a regular boot? Folders of same name may exist in the boot ramdisk and these are merged with system folders after boot.
3. Try wiping cache between reboots and see if that changes any of your observations.
Click to expand...
Click to collapse
Good questions. They got me thinking more about how this could possibly work.
I had a look at the cache and there's definitely no copy of the system hiding there.
I also unpacked the ramdisk in the boot image and it had nothing in system. Furthermore, the boot position is only 64 MB, no where near enough to hold the system.
Then I installed Magisk so that I could browse around the phone's partitions and take copies.
I learnt two things from this:
1. If there's a second copy of the system there are only three partitions large enough to hold it (/proc/partitions shows the sizes in 1 kB blocks). The system is about 1 GB. There is space in the system partition (sde20) for 3 GB. There's also space in the data partition (sca15). And there's space in the major partition holding the modems (sdf).
I could eliminate the data partition by formatting it but restoring the internal storage (sdcard) is such a a pain.
So I'll just accept that there is space for a copy, but I'm unlikely to find out exactly where.
2. When I had Magisk installed installed and the system boot, I added a folder and file to /system/priv-app using a file manager (so not using TWRP). I then booted into recovery, flashed the stock boot image, and rebooted. I was expecting it to fail dm-verity (modified system) but it didn't. After booting up there's no evidence of the folder I added to priv-app.
And if I restore the Magisk boot image then the additions show up again.
I'm actually very impressed with how the stock system (kernel, recovery, system) protects itself from modification. Very cool!

TWRP: persistent decryption of /data

Hello and thanx for your attention. Can't fix my problem. Or I read the wrong threads. Anyway, i would appreciate your help.
Installed twrp r20, rebooted in recovery, flashed magisk 19.1 or su 2.82. First everything's fine, twrp's backup shows some Mb in /data (caused by magisk or su). So decryption is working at that point. Then, after booting into system and doing some settings, root is still there (rootchecker), but back to twrp there will be /data again with 0MB.
As i understand booting re-encrypts /data from f2fs to emmc. Anyone a hint? Main purpose of twrp for me is taking backups (before trying custom roms)
Running stock oreo 8.1.0 Europe with 01.02.19 sec patches
Thanx in advance

Found solution. Maybe it's for interest of TWRP newbies like me...
TWRP decrypts just in time, if you use the PIN of your android's LOCK SCREEN (settings-safety) at start. You will see full /data and can run a nandroid backup. Rebooting to system then will encrypt /data again.
A had issues using a password for lock screen, so better use PIN.

ROG 2 phone soft bricked

Hello,
today I did have a strange experience with my ROG 2 and my best guess is that there is some UFS problem, but a second opinion or ideas are welcome.
During a bike ride when I was wifi scanning (apps: "Tower collector", "Radio Beacon"), navigating and listening to an audio book, the phone just went dark. I thought from previous experience on a Note 3 that it might have overheated. Pretty much stress proofed from the previous phone.
Yes - it was warm in its bike pocket but really not overly hot.
The phone is an ebay buy 2 months old and has been ever since with omnirom, stable so far. I only noticed that the RGB LED here has no blue light, but I plainly did not care.
I tried to boot it after some 10 minutes again and the phone would not go past its omnirom boot screen until it reboots after some time, boot loops.
30 Minutes later at home I wondered then what is going on, and I copied off the TWRP backup from the phone I took two days ago, just in case.
I then tried to restore the same backup, but the phone switched off during restore after ~30%. This was reproducible, so I thought this may be something with the backup, maybe I cannot restore a partition. When I restore I had all partitions marked and I tested them one by one. The restore of single partitions worked, one by one, except vendor as it was marked read only and data as it failed unpacking (my recent backup then is dead?).
I then tried formatting the partitions, so "data", originally f2fs. I lack experience with journal recovery on f2fs so went to ext4. System was ext4 and was just wiped. I lost of course other data on the internal storage so tried to restore again with my copied backup. It restores, but it cannot boot and just bootloops. I now formatted all partitions, including vendor.
Finally, I tried downloading omnirom again and installed it. It won't boot, it doesn't even get to the boot animation, but just boot loops.
I reformatted data back to f2fs. But no change here.
Trying more: lineageos won't flash for unknown reasons, it immediately dies as "Error installing zip file". Checksum of the downloaded zip is correct.
I downloaded a stock rom and installed it. This is now the best result so far - It does want to boot.
Here I get a boot animation and this incredibly lame "tching" sound (it is a phone, not a sword...). But it also stops there and never continues. Yes, first boot takes longer, but not 10 minutes.
Any ideas what else to try with this phone?
So far, I can boot twrp via sideload and interact with it fine. But that will be it; ran out of ideas.
Happy for suggestions.
Gaya

Use raw firmware to restore everything.
Install latest firmware zip on both slots.
After installing custom roms go to wipe -> format data by typing yes. Otherwise rom wont boot

thanks for getting back, If by raw firmware you meant the ASUS stock, I did. Not sure why data wipe after installation or double install to a/b partition would make a difference, but in the end I am new to this a/b concept, looks though like standard dual boot to me. Tried it, but no difference.
- installed asus firmware to inactive B
- switched to B partition
- installed asus firmware to inactive A
- wiped data
- started, so far same behaviour after 15 minutes of waiting (boot animation with sound, then it repeats boot animation until ...).

There are Two kind of rom raw firmware (used to restore bricked device) and recovery rom (zip file we use for update)
Raw firmware will flash ROM to both the slots, while recovery rom only flash to one slot. So you need to Only select reboot to recovery after flashing ROM to switch to the updated slot.
No, stock rom is not exactly raw firmware. RAW firmware uses EDL mode (in bootloader) to flash the stock rom. Download A10 raw from here version .90.
when extracting it you will see some files.
Steps To flash Raw:
* enable usb debugging in phone.
*connect the phone via side port to pc
open command prompt and run this command
adb devices
adb reboot bootloader
Now go to the folder where you extracted the raw firmware & run "flashall_AFT.cmd" as admin
wait [there will be no output]. After 15 -20 mins your device should boot. If you have any old version stock rom data the phone will carry the data to new version. If you have any custom rom/ updated version of stock rom data, it will ask to factory reset, so do that.
wiping is not exactly formatting so do it the right way
Why format: the one where you format by typing "yes" .If you switch between Roms ( stock to custom or vice versa) and go back to older versions (v .100 to .60) the old/previous rom data cant be used with new one so you must format data.
when formatting is not necessary : If you want to upgrade both stock images (version .90 to .100) & custom rom (v 1 to 1.2) i.e., flashing stock rom and then custom rom over it, you dont need to format data because you can reuse the data from custom rom to updated custom rom.
A/B device use two partition instead of one. so the upgrade can happen in the background. On restart you will switched to updated slot. So room for error is less.

The wiping here should be the same as formatting, as it is running the mke2fs (as per TWRP settings). But raw rom I do not have (I believe).
The link you have there seems broken, could you repost it again?
I did download the stock ROM earlier from ASUS directly, to not violate policies, HTTP links etc, here is only the path on asus . com
pub/ASUS/ZenFone/ZS660KL/UL-ASUS_I001_1-ASUS-17.0240.2103.75-1.1.229-user.zip
That is the one I installed via recovery. Am not sure what is in your mentioned flashall_AFT.cmd though, but suspect some adb sideload at least.

I eventually succeeded, but of course would liek to know
1) why
2) what happened?
I did follow a video about flashing the stock rom, basically as you explained (factory reset and data wipe), twice to a and b partition. That made the device bootable. Why is this needed?
I tested wiping system again (I am used to doing clean flashes) and installed omnirom again, and it failed booting.
I installed again the a/b with stocks, factory reset and data wipe and installed omnirom as dirty flash. All is well.
Now I was able to restore my backup finally without the device switching off and it did not complain about the data backup. So finally I am with my phone again rom and copy data to my fresh partition.
as to 1) why?
I understand a/b partition as sort of windows/linux dual boot with a more separate bootloader maybe. So I do not see the point in flashing the stock rom twice or in rendering the device unbootable when wiping system.
and as 2) what happened.
I may only guess: I did an omnirom upgrade 2 days earlier that worked fine and was the reason for my nandroid.
During my ride, the phone had some whateverissue and rebooted. I am unsure whether i tested booting but assume that after the upgrade it flashed to the other partition and it was not bootable. It does not make sense as this would make a/B partitions rather hard for custom rom makers, e.g. people complaining all the time.
Other guess: there was a file system issue with f2fs. Problem with data partition seems to cause bigger issues.
When I flash to ext4 after testing the bootable rom with a wiped data, it would not boot anymore. After factory reset again, it mke2fs the data partition again, back to f2fs and the device booted again happily.
Thanks for the help. Happy to know/learn more about this issue, as I would love to prevent or handle them quicker with more of I know what I'm doing.

Android Dual Partition (A/B) is made for seamless updates i.e, Dual system/vendor partition but uses same data partition. Lets say you are currently in slot A when you apply system update the slot B gets updated. As always rebooting the device switches to the B partition after update. & further update flashes the system to the A partition.
Basically there is no need to flash stock rom twice, unless you are coming from stock [one partition might be in higher firmware version than other] or there is new stock version with some minor/major upgrades to firmware files.
Our custom ROMs are not stand alone, Mostly it only replaces the system files and keep the vendor same as stock. (also this keeps the ROM update file size to be minimum)
you might even have different version of Android in A/B partition.
Here is a scenario on How A/B works:
Say you are currently using your device in B-slot and A9 so partition on slot-A will be A9 partition slot-B be A9. After that you are doing system update to A10 from System update (not via TWRP)
now you will have A10 on slot-A and A9 on slot-B.
then you want to go to custom rom, so you flashed say omni on A-slot and rebooted & it will surely work.
After that you are using inbuild system update from custom rom any applied it. now the system update will overwrite the A9's system files but (the device specifically needs A10s vendor to work properly). Now comes the fun part i.e., soft brick, boot looping, and corrupt images
That's why you have to flash latest stock to both A and B slots, and overwrite them all with system files from custom rom (also should be flashed once in slots A and B) to get neat experience from custom ROMs.
If you understand what was written above, then you will know the reason behind soft brick.
stock rom flashed only once (firmware image variation may affect stability)
custom rom only flashed in one slot (switching slot will boot loop device)
Not using Reboot to recovery to flash (you will be flashing to the same slot over and over & thus rebooting will boot loop)
Not formatting data ( Just Maybe, your custom ROM and stock uses different file system for data partition)
For Raw files search "ASUS rog 2 RAW firmware images" those files will be around 3 GB in size.