Phone (Zenfone 6 ZS630KL) keeps booting into csc fastboot mode

[Yavych]

Hello. Today, my wife's phone stopped responding to anything out of blue. I did a forced reboot (Vol down + power) and it rebooted and worked fine for a bit. Seeing as Android 10 was out, I dled fota file and flashed it via recovery from SD card, like I usually do. It flashed successfully and then rebooted. Once it booted, after a few seconds it hanged and became unresponsive again. Forced reboot once again, except this time it booted into a fastboot mode on its own and here lies there problem:
- going through an option to get into recovery mode doesn't help as it goes back into fastboot mode again
- rebooting through cmd doesn't help either
- pressing start just returns to fastboot mode - shutting it down through an option in fastboot and then turning it on still yields the same result.
Basically, whenever phone turns on, it goes into a fastboot mode whether you want it or not.
Seems like update failed to flash into slot B
(bootloader) has-slot:system:yes
(bootloader) current-slot:a
(bootloader) has-slot:boot:yes
(bootloader) slot-retry-count:b:6
(bootloader) slot-unbootable:b:yes
(bootloader) slot-successful:b:yes
(bootloader) slot-retry-count:a:7
(bootloader) slot-unbootable:a:no
(bootloader) slot-successful:a:yes
(bootloader) slot-count:2
What can I do about this?

[cobben]

Can you copy the FOTA File to the phone while it is in fastboot mode?
If you can, try just rebooting it then - it might find the file and try to install it all on its own.

[Yavych]

cobben

Can you copy the FOTA File to the phone while it is in fastboot mode?

If you can, try just rebooting it then - it might find the file and try to install it all on its own.

View post

It's in the root of SD card which phone usually detects when it's on. I can't copy it to the internal storage while it's in a fastboot mode

[Yavych · Accepted solution]

Okay, so I fixed it.
I flashed service/raw fw through fastboot, commenting out userdata formatting part of the flashall_aft script (fastboot -w). After this, I was able to access recovery mode. In recovery mode, I flashed build 16.1220.1909.194 and then 17.1810.1910.63 from my SD card and phone came alive, while retaining all the data.
Perhaps, this information will help someone who will encounter the same situation.

[Yavych]

Well, issue has come back, again, out of blue. Phone was lying on the table overnight and in the morning became unresponsive. This time, however, force reboot doesn't help. Device is stuck in QDLoader  mode. Perhaps it's one of those that had a defective mother board and should be replaced by ASUS? Is there any ASUS support center that handles these phones in Ukraine?

[ColorSage]

I would suggest installing a zip through recovery. You don't need unlocked bootloader for that. If your phone's bricked again and has problems with bootloader you will need RMA though