Simple things first
1. Unplug coach from house, does the house breaker trip. If yes, it is house wiring. If no, it is coach wiring.
2. Flip to off all breakers in the coach, does the house beaker trip? If yes, it is something between the end of the cord and the coach breaker box. If no, then it is a circuit in the coach.
3. Flip on the coach main breaker but leave off other breakers, does the house breaker trip? If yes, it is the coach breaker box. If no, then it is a circuit in the coach.
4. Flip on and then off one coach circuit at a time until the house breaker trips. When it does, you have found the coach circuit that is causing the problem.
5. If the house breaker never trips in #4 above, but does trip when all the circuits are on, then I suspect you are overloading the 40 amp house circuit.