After having downgraded a phone from 8.9.3.x to a firmware version < 18.104.22.168 the phone is not able to perform any upgrade / downgrade.
The phone just reboots, the normal update procedure doesn't start. At the end of the boot-up the phone shows a "Firmware update failed" error.
- Any phone running an 8.9.3.x or higher firmware should not be downgraded to a version < 22.214.171.124.
- This may lead to a deadlock situation where the firmware works, but the phone cannot be updated anymore, except with a network recovery.
- All versions < 126.96.36.199 are affected by this update procedure issue.
- If the downgrade is mandatory, use the 188.8.131.52 as an intermediate firmware downgrade step, before you finally install the desired/known as affected version!