I had a similar problem on my 2015 Vista 27N. The top breaker in the breaker box was not making good connection to the bus bar inside the breaker box and it would cause the breaker to heat up whenever there was a big load flowing thru, like the AC running or the hot water heater running on electric.. The heat would cause the 30 amp breaker to trip. The ears that push over the bus bar were not making good contact causing the heating. The overheating also damaged the breaker's plastic housing making the situation worse over time.
I bought an exact replacement breaker and replaced it. This resolved the problem. It has not re-occured. The bus bar was a little discolored but I did not have to buy a whole new box housing.
Replacement Breaker on Amazon.com