I have had the same issue. My inverter is above the propane tank and the GFI on the inverter kept tripping when shore power is disconnected. Had a technician come look at it and of course it started working when he looked at it. It worked perfectly yesterday when traveling 400 miles. One thing I did was remove the black panel so the technician could look at it, and never reinstalled it. Not sure if the black panel had anything to do with the GFI tripping, but I am going to leave it off, not to jinx it.
2014 Forest River Georgetown XL 378TS