Can't really troubleshoot it without knowing the voltage and current when it trips. When voltage decreases, current increases. The breaker trips when the current goes high enough to exceed the trip rating of the circuit breaker. Don't change the circuit breaker with a higher rated one. They are there to protect the wiring from overheating and burning down the trailer. If voltage and current is normal for that circuit, replace the circuit breaker with the same current rating. They do wear out. Especially when they experience a few overload trips.
