My guy, you are the best. wanted to let you know the PC has been fixed and this can be closed. It must be hard to help internet strangers so, I applaud your efforts.
The issue ended up being two things:
- The user had 4 sticks of ram, 1 of which had gone bad. We eliminated that via MEMTEST86
- The user was running a 5900x on an AMD stock cooler intended for 3000 series low end CPU. It was overheating! Replacing with a proper aftermarket cooler and its much more stable now.