I have turned the main breaker off in the RV and the house breaker still trips. I have tried different extension cords and adapters but breaker still trips. I have even replaced the gfi outlet but still have same results. I have used the same outlet and extension cords with other devices and they work fine. We had no issues while camping but had to plug into 30 amp service. Scratching my head at this point. Any suggestions?
With the main breaker OFF in the RV, I wouldn't think anything downstream from the main could be causing the problem.
If we assume your extension cords, adapters, and new GFCI outlet in the house are all ok, then that leaves the RV shore power cord, the connector it plugs into, the wires from that connector to the main breaker panel, AND if you have generator prep, the transfer switch. It's even possible you could have a loose or damaged connection on the back side of the main breaker panel.
If you have a transfer switch, even with the main circuit breaker OFF, the transfer switch uses a small amount of power. There is a circuit board that takes power from L1 and fires the contactors to make a connection.
I would start with the shore power cord and the connector it plugs into. Look for discoloration, loose components, and wire damage.
If that all looks ok, with the coach unplugged, check the transfer switch. With power disconnected, remove the top cover and check that connections are tight and that there's no discoloration or other sign of damage.
If that looks good, with power disconnected, take out the screws holding the main breaker panel and gently pull it away from the wall. Inspect the backside connections.