I have a microwave that works great except when the temperature outside is something like 15 degrees F or cooler outside. When this is the case, it more or less reliably trips the GFCI breaker in my basement, requiring me to turn it back on to try to get a few more seconds of heating out of it.
This never happens when the weather is warmer.
I’m only able to do proper tests when it is cold like this. What i did today was after the breaker tripped and I flipped it back on, I plugged the microwave in with a kill-a-watt meter in order to monitor the voltage. I conducted the same test (heating one hot pocket) and it completed a full minute without incident. So it may be possible that the kill-a-watt meter introduced some difference that prevents it from tripping now. Although, this is only one data point.
I just wonder what are some other things that I can test. And if I plug the microwave on a different circuit (having a regular breaker) it runs fine.