Facing this exact issue. I'm currently on a barely usable OS (9.5.4) and I'm not sure how to wipe and reinstall 9.5.4. Sideloading the full zip on TWRP doesn't seem to be working. If I try to install the 9.5.4 boot image from this thread. I get a recovery boot loop (It just boots to recovery even if I choose to boot to system). The only way I can boot my phone is by using the TWRP boot image from
https://forum.xda-developers.com/on...nt/recovery-unofficial-twrp-recovery-t3931322 and with it, I get no WiFi and making phone calls hangs my phone.
During boot, logcat shows a lot of errors related to the adsp daemon crash restarting as well, if that's at all relevant.
What I did to get into this mess from a rooted stable 9.5.3 (on ElementalX kernel):
Install update from Settings (Update Engine)
Get the boot image from here and patch with Magisk
Flash the patched image from fastboot
Got a recovery boot loop there and so I flashed the TWRP boot image
Tried to flash Magisk through side load on TWRP
Still recovery boot loop so I flashed the TWRP boot image again
I really dropped the ball on this one. Any help would be appreciated.
UPDATE 1:
I've worsened the situation by trying to wipe system from TWRP and then side loading the ROM. The installation finished at ~47% on the sideload progress. Going to try @mauronofrio 's fastboot images from
https://forum.xda-developers.com/oneplus-7-pro/how-to/rom-stock-fastboot-roms-oneplus-7-pro-t3931424
Also noticed that BOOTLOADER VERSION and BASEBAND VERSION show up as empty in the bootloader.