Golly! First of all, the situation and what I will be doing to solve.
When I first plug in to the GFI outlet (any GFI), the outlet does NOT trip. That would indicate that all is fine through the cord, adaptors and plugs up to the Surge Guard. It is only after the 2 and a half minute delay when the Surge Guard allows the power to flow through does the GFI trip.
I will first unplug all appliances and disconnect all AC devices including the Water heater (on its own breaker), refrigerator, and converter. I have no transfer switch.
If that fails to solve I will proceed to bypass the Surge Guard which might have some leakage, by putting jumpers around the unit to allow voltage to flow to the coach immediately, without the delay. If I get the GFI trip then I have eliminated the Surge Guard as a problem.
I will then proceed to remove the neutrals one at a time to attempt an isolation to a specific circuit. It is my hope that I should find the problem this way.
I have really enjoyed reading all the suggestions and expertise here and have learned more than I thought. For instance, I did not know that a neutral to ground would trip a ground fault.