Assuming all of your adapters and plugs are clean and tight, and your GFI outlet is good, the next step is to check the actual voltage with a meter at the outlet any thing less than 105V is no good 110-125v is what you need (remember voltage drop if you are useing extension cords low voltage= high amp draw). Then turn all of the breakers off in the 120v panel in the M/H including the main, make sure ALL electrical loads are off in the coach, UNPLUG the coach turn off the inverter if you have one, make sure the generator is off. Check ALL connections in the panel and T/fer S/W make sure they are clean and tight (this part of the yearly maint. on my coach). Put every thing back togather turn the main on, turn on breakers on at a time when the GFI trips there is the circuit with the problem could be a a light fixture bad wire bad or loose somewhere. If you are not comfortable working with AC voltage and a meter you might should call an electrican who has RV knowledge before the smoke gets out of something, cause the smoke is hard to put back in the wires once it's out.