My built-in mircowave is on the same circuit as our kitchen lights. Every now and then, the microwave will cause a trip. Only the breaker doesn't switch off. It's still in the on position but an off/on flip gets things working again. It doesn't seem to matter if the lights are on or off and the microwave mode (defrost vs high power). That said, it does seem to happen more frequently in the colder months. I've replaced the breaker and it made no difference. Does anyone have an idea of what the cause and fix are?