This is a result of trying to play games in wine and dxvk.
It used to work, but the latest mesa git fails.
Games that fails are:
Assassin's creed odyssey
Devil May Cry 5

Both these games get through the title sequences, but fail when you reach the
actual game play. The GPU hangs and tries to reset, but fails to reset.

So, there are two problems:
1) Why does it hang in the first place
2) Why does it fail to recover and reset itself.

I can ssh into the PC.
poweroff   <-  Attempts to power off but never actually reaches off state.
echo b > /proc/sysrq-trigger    <-  reboots the box, and everything is then ok
again, so long as one does not try to play a game.