If your coach has an EMS(energy management system) this is normal. If the system detects that there is not enough power available in certain circuits, it will shed power.
Just because you are hooked to a 50 amp service that does not mean that you have all of that power available.
With your inverter, you have what is known as "pass-through" current/wattage. In other words, if you have a 2000 watt inverter, that is the MAXIMUM amount of power that can be used on your inverter circuits. That is probably why your inverter circuit breaker tripped. You were exceeding your inverter pass-through current, even tho you were well below your main circuit breaker capacity.
I have never tripped my main or even one of my separate circuit breakers but I have tripped my inverter breaker a few times.