[Huawei P9 Lite Questions & Answers] Alc@h0l1k81n05avr:
Hello there. I had recently updated my p9 lite to android nougat from VNS-L31C440B132 single sim to VNS-L31C440B380 with the official uk ee firmware and was absolutely in love with it so far. I had installed magisk and viper4audio with but i wanted to see what other mods like dolby atmos and xtrememusic could do so i added the audio modification library mod so i use multiple mods at once. Dolby Atmos was pretty unresponsive and time i did manage to open it it immediately crashed so i unistalled it and tried out xtrememusic and this is where the problems really began. when i tried to play videos on apps like facebook and youtube they wouldn't load, the video would buffer but it didn't play and on facebook some videos did load and strangely music apps like would play music but i couldn’t hear anything but sound came out of my phone’s music player, i thought the sound mod was messing up so i looked for an uninstaller and found one androidfile host. I booted into TWRP (Openkirin edition), flashed it, and rebooted. I was met with a black screen and the phone was trapped in a bootloop and booted to a screen that told me to do a factory reset which then led into my tarp;I realised the phone got soft-bricked I panicked at this point and the reset didn’t and went back into twrp to try and flash any other versions of the mods to see if it would clear up the problem but it didn’t. I tried to format data but was met with: ‘mkfs.f2fs -t 0 /dev/block/mmcblk0p49 process ended with error: 255’ so I had to go back then i tried to see if i could dirty flash the rom as i still the original firmware i used to update my phone and the stock rom before the update, should’ve realised that wasn’t the best idea; I failed trying to install the main package but the ota update installed with no problems. I booted up the it still wasn’t loading (at this point I had already done a factory reset via twrp and data cache and dalvik) so i decided to see if i could clear the system and then re-install the b380 rom. every attempt i made was unsuccessful as twrp kept saying ‘failed to mount data (device or resource busy)’ or other problems like ‘could not mount /data and unable to find crypto footer’. Eventually I got to where I am now by completely erasing cache, data, system and storage. As there’s absolutely nothing on the phone now as i am on B380 can i just push the nougat firmware to /sdcard/ via adb on my mac and install it as is it or failing that is there any way I can downgrade to L31C440B132? I know to downgrade you need to download an intermediary package specific to your phone build but i looked and I can’t find one for the L31C440 range; I’ve checked Huawei’s official uk support site but the firmware is listed as C900B3000 and my build number isn’t listed. I’m worried that if i do manage to rollback to that specific firmware I won’t be able to restore my VNS-L31C440B132 rom to the phone as it may be rendered incompatible. At the very least I want to know if I can restore the from the nougat rom + update or a sim toolkit i can use to change my oeminfo to C440 and then install my stock firmware. Another thing this is the ota package i flashed: update_data_full_VNS-L11_ee_gb.zip, it says VNS-L11; please let me know if that is going to complicate restoring the rom. Thank you.

Update: I have managed to repair my data partition by doing another factory reset and changing the file system from f2fs to ext4 and the phone is seemingly in a normal state but every time I try to reinstall the main update.app package i get:

Updating partition details...

..done

Installing zip file '/sdcard/update.zip'

Checking for MD5 file...

Skipping MD5 check: no MD5 file found

Removing unneeded files...

Removing empty directorys...

Patching system files...

Unpacking new files...

add link type file...

write radio image...

32K crc checked failure

E:unknown command [errno]

update_huawei_pkg_from_ota_zip: update package from zip failed

Updater process ended with ERROR: 7

Error installing zip file '/sdcard/update.zip'

Updating partition details...

...done

However the other file, update_data_full_VNS-L11_ee_gb.zip installs just fine:

Updating partition details...

..done

Installing zip file ‘/sdcard/update_data_full_VNS-L11_ee_gb.zip’

Checking for MD5 file...

Skipping MD5 check: no MD5 file found

Verifying current userdata…

mountencrypt: failed to mount /data: Success

Removing unneeded files...

Removing empty directorys...

Patching system files...

Unpacking new files...

add link type file...

write radio image...

script succeeded: result was []

Updating partition details...

...done

I'm completely stuck now and really don't know where to go from here as only the other smaller package seems to install but when i try the reboot option it gives me ’no os installed! are you sure you want to reboot?’; should i change the data partition filesystem back to f2fs or is something else wrong with the install? This has been incredibly fruatrating for me. back when i was on marshmallow if i had problems rom-wise, all i had to do was advanced wipe and then just reflash my L31C440B132 stock rom with no problems but now i'm stuck in a real mess as the original rom which i updated to 7.0 is also gone so I've basically got a phone that's upgraded to C440B380 with no firmware at all; I can still boot into twrp but it can't really do anything significant atm. I would like to try debranding it through the rollback package on the official huawei support site but i'm not sure how I can convert my phone's oem info back to VNS-L31 single-sim C440 afterwards. any advice you guys have would be extremely helpful now, especially finding a rollback package to match my build number.