[OnePlus 8T Questions & Answers] Dorakkaru:
Hello

I created an account to ask for help recovering my device to which I am really tired of trying stuff without any result

I know some of the actions I am going to mention in this post are going to cause insurmountable amounts of cringe to a lot of the community, but that's how things went

First the phone

It is a OnePlus 8T T-Mobile variant I bought secondhand (no warranty)

When I first got the device I struggled a bit to root it (I love my devices rooted) but managed to do so using this T-Mobile to EU version of the MSMTool

Everything went fine, managed to convert my device, unlock it, and root it

At this time I also took the precaution of making a backup of my persist, modemst1, modemst2 and modemdump partitions

It was working fine except for a little bug in the NFC reader

Some time passed and I got a notification about a new Oxygen update that supposedly fixed some NFC bugs, excitedly I tried to install it only to come to an error, I tried a lot of things to install it unsuccessfully, finally I tried unrooting the device thinking that may be the problem, but nope

After failing to install the update I wanted to go back to rooting my device (again) but dumb me forgot how I did the procedure the last time, so i went like "yeah, I think I just went into fastboot and flashed the magisk boot.img....right?", nope, I got stuck into a bootloop

In my desperation to recover my device without wiping it I went scrambling into OrangeFox Recovery and started clicking things, and at some point I changed the Active Partition Slot

The device went from bootlooping to flickering the logo on and off and not even entering Recovery or Fastboot, only EDL

I tried using MSMTool again, not caring about wiping it anymore, but kept getting an "Automatic DDR detection failed" error no matter how many times I tried

I even opened the device to access the EDL test points easier as instructed by this post

I came across this little EDL program that allows you to directly issue commands to the Qualcomm chip while in EDL mode and wrongly tried writing the image files of the Global version

It took me a while to modify the EDL python script because it was trying to generate a token based on a mismatched ID and Key, but I managed to return its proper matched ID / Key

I tried using the EDL program again to this time write the correct T-Mobile image files (one by one as indicated by the Settings.xml file and applying the patches afterward as indicated by the same file) and I got a bit of an advancement, now the screen did not flicker on and off anymore but displayed an "SMT Download Failed" error and also restored access to Fastboot!

I have tried using MSMTool again but now I keep getting "No valid trg ID" with the log showing the following

I believe I have messed the phone so bad and the IDs are so mismatched that MSMTool doesn't knows what the heck it is, I have tried using the SMT Download Mode (I am fully aware this is going to wipe the IMEI, MEID, Widevine certificates and whatnot, but at least I have EFS backups), but it asks for some MES Settings I don't know how to fill

View attachment 5974555

It's been quite an odyssey to me, I beg if anyone can share any info on what to do to save this device OR if there is really no remedy for this to at least finally give up trying to repair it

Thank you for reading!