For some time my freezer at home was behaving strangely. Going to alarm mode because of temperature rising, but then restarting normal freezing operations when setting super-freeze mode on the control panel. It was then working correctly for one or two days and then going to alarm mode again.
Weird... obviously not a mechanical problem because super-freeze quickly brought the temperature to -30°C. A malfunctioning relay? Let's open the beast.
No relay there. All electronics, and... a tiny fly, less that 2 millimeters long, that got burnt between a transistor and a LED pins on the control panel and was perturbating the temparature regulation.
I removed the dead body of the poor fly, put back together the freezer pieces, and there we go. The freezer has been freezing normally again for about one week now!
A nice reminder for us computer geeks of where software bugs come from!