Modem/SIM/Wireless broken when returning to Stock MIUI from Custom ROM

[mymi6]

Hello,

I was using LineageOS since the first day I got the phone. I performed the Android12 upgrade however it was not fully usable yet so I decided to flash my backup. Then there followed some major backup restore issues which forced me do revert all the way back to Stock MIUI and start fresh.

I downloaded the latest stable global firmware from here flashed it using MiFlash 2020.3.14.0, it bootet up like expected, however there was no wireless nor sim card detected. After enabling usb debugging I checked the log and found concerning entries (see attached log.txt). I did also try latest stable China MIUI also boots up but no wireless either.

It is complaining about /boot/modem_fsg_oem_1 and /boot/modem_fsg_oem_2 anyone got an idea what the problem could be or how I can debug it further?

Thanks in advance.

 

[mymi6]

Oh boy, what an adventure.

Lucky me found a nandroid backup file I took when I first got the phone which had the EFS partitions in it. I had to strip them out of the full backup.ab file though. Luckily the ab-fileformat is very simple, just a bunch of 512 byte chuncks, and I was able to quickly hack together a python script which removed all other partitions from it. Twrpabx did not work for me. Flashing went flawlessly followed by a successfull MiUI global flash with now working wireless and modem.

I'm still not sure what initally cuased the partition corruptions. I guess it had something to do with TWRP, since at the point of writing it was not yet capable of decrypting Android12 partitions. I'm not really sure, since in the past I've never had any problems restoring about 50 backups.

Maybe I'll now get the Android11 backup up and running aswell like I initially planned, but thats a topic for another day.