It most often seems to be the power management/charge/USB-C chip, with no particular pattern other than "playing a demanding game". Doesn't seem to matter whether plugged in or on battery, official charger or other USB-C charger or dock. I even had it happen to my own Steam Deck (while playing Minecraft of all things) which I sent into Valve and they replaced.

I haven't been able to investigate it too much but last I looked at the data sheet for that chip it seems like there's no way it should have a hole blown in it unless something was designed wrong.