I bought a cheap electric heater from Lowe's a few years ago. It surprised me greatly because it would occasionally rewire itself. It had a rotating switch with Off, Fan, Low Heat and High Heat settings, but once in a while these switch settings would change. Like, Low Heat would actually by the Fan setting, Off would actually be the High Heat setting etc. It turns out the rotating switch just travelled over some printed solder lines and occasionally these would melt and re-form into new positions.

How there was not an epidemic of homes burning down because of these things is a mystery. But there's just no way engineers could have ever guessed something like this would happen.