I've noticed that our microwave's performance tails off alarmingly during times of Silly Oak vole shortage. Which is mostly in the evenings and around lunchtime, obviously. It took 7 minutes, 6 seconds[1] to almost completely fail to defrost a curry the other day.
[1] Throwback to our previous - much better - microwave, which in its twilight years suffered from a corroded membrane keypad, with the effect that the '0', '2' '5' and 'auto defrost' buttons were non-functional[2]. As a result we've developed some peculiar habits when it comes to arbitrary durations for microwaving things.
[2] There was a brief reprive when Hananananah The Astronononmer[3] and I carefully peeled it apart and applied conductive paint to the b0rked bit.
[3] Optical, so has entirely normal attitudes towards microwave ovens.