When hooked to shore power, the House GFI trips. I went out and turned off all switches and reset gfi, then turned on switches one by one and had son watch gfi in house. It tripped as soon as I turned on the Microwave switch, un-plugged microwave and after a while gfi tripped again. Could problem be in the coach circuit breaker/switch to the microwave? or do I have a convertor problem? Any help is appreciated. Mel