Yeah. I wrote the code for a controller that managed the temperature of a lubricant. The heater was a propane-fired burner that was mounted on the same skid. Every so often we'd get a random reboot. Finally, when it was very quiet, I heard a soft 'tic' just before I noticed that the CPU had rebooted again. EMI from the spark gap that ignited the propane was coupling back into the I/O lines and would occasionally reset the CPU.

One of those things where if it had happened 100% of the time we'd have figured it out quickly. But it was so infrequent that no one thought of that as a cause.