Comment by TheFlyingFish

I once managed to trigger what I think was a race condition in a microwave's beep routine. It was one of the type that does a single long beep rather than individual beeps, and like most it would cut the beep short when you opened the door. But one time, one single time, I managed to open the door PRECISELY as the timer finished, and the beep just didn't stop. I finally closed and opened the door after maybe 30 seconds, and that stopped it.

I was never able to trigger it again, so I have no idea whether it was a race condition or some other random one-in-a-million happenstance, but it makes a fun theory at least.