Well, I just spent the last 45 mins with it open and every single last screw needed from half a turn to 2 or 3 turns. I also saw a 7812 that I couldn't get to without a lot of removal of parts but it had a different screw attaching it to the heatsink AND the screw was plastic. Obviously this was changed at some point but with the thin layer of dust all over the parts and board it was not recently.
There was a power transistor on both sides of the back and the left one had a thermal pad but the right side one had none so I added thermal grease just in case.
If it continues to make the thermal pop it will just have to break to figure out what to replace.