Causes for breaker tripping
While I have not looked at RV services with 50Amp service, it is my understanding that all they do is take a 50Amp 240v receptacle and split that into two 120V circuits, each using the common neutral and ground, but having separate conductors for the hot wire. If you had two 30Amp panels in your trailer each could be fed from one of these circuits. Then you could separate the loads in your trailer into each of the panels, trying to balance them when you do.
You mention this occuring while the weather is hot. While we think of the heat necessary to trip a breaker being produced by the load on the circuit, other sources can contribute to the heat produced. Others have mentioned the 20Amp half of the twin 20-30Amp breaker being under heavy load, loose or corroded terminals, tripping at the pedestal in the campground and the weakening of the trip unit. Ambient heat can play a big role in causing a trip. If it is hot in your trailer, if the pedestal is in direct sunlight, especially a western exposure, or just about anything else that causes a higher ambient temperature will affect the load carrying capacity of a circuit breaker.