I have the same inverter as you do. If the transfer switch clicks(make sure this is happening) when you are hooked to shore power then it appears that you are losing power as it comes in to your coach. On the front or side of some Xantrex inverters(the D models) are THREE circuit breakers. The two lever type circuit breakers(may be on the front or side) control the power in to your coach and the single push button circuit breaker (the white one with the "20" on it)supplies power to the battery charger portion of your inverter.
The two lever type circuit breakers supply power to your main circuit breaker in your electrical panel inside the coach. There is also power that comes in to your coach that bypasses your inverter and goes directly to your AC and SOMETIMES to the microwave outlet and electric water heater.
Once the power goes through your inverter or if it bypasses your inverter, that electric is run through your main electric panel and routed out to the separate circuits managed by individual circuit breakers. It is unusual but circuit breakers do go bad.
You need to start at the beginning and check everything from the shore power pole on in.