Your microwave probably needs fixing
If you have a microwave-oven combo that was commonly installed in our homes, then you will want to follow this link for more information regarding a factory recall.
The short details are: The door switch in the microwave oven can overheat and ignite plastic components in the control area. You should stop using the microwave in the micro-oven combo immediately. You may continue to use the lower thermal oven.
Thanks to Beth M. for letting us know about this recall!