You don’t often think about it, but many appliances/tools/toys/etc that we think of as ‘hardware’ have many ‘software’ components – and almost all software has bugs or idiosyncrasies. Unless you think a bit outside of the box, you hopefully won’t notice. This is really a good thing – a bug in your microwave probably won’t kill you. A bug in your car, on the other hand, really can kill you.
The oddity I’ve noticed in my microwave is that I can set it for any number of seconds. So, I can heat my food for 0:60, 1:00, 0:90, 1:30, etc. I can even set it for 1:99. It doesn’t reduce the utility or safety of the appliance, but it might not be what you expect. This demonstrates the problem: try something the designers didn’t expect and you will get an unexpected result. It happens a lot.