I have the OnePlus 9 T-Mobile variant upgraded to Android 12. I've noticed a few bugs after the update.
1. The new messaging app displays text in the wrong order and shows incorrect dates text are received and/or sent.
2. Incorrect processor 888 snapdragon is correct. But is showing 855 snapdragon.
3. Low volume/muffled calls. I've checked with a few other phones, no issues. Seems to to only be affected by the OnePlus 9 T-Mobile variant.