First there are two devices people confuse all the time GFCI and Circuit breaker.. They have two things in common
1: They are electrical devices
2: They can shut off power if they detect a condition they are designed to detect
A circuit breaker detects excess current. And will trip if the current rating is exceeded (Too much load)
A GFCI detects ground faults, and will trip if a ground fault is detected.
A GFCI is kind of like a teeter-totter If the two kids on the teeter totter are exactly the same weight, the thing is balanced, but what happens if one kid is 50 pounds and the other is 100.. Answer the heavy end hits the ground, fast.
GFCI's work like this. They monitor the relationship between the current in the HOT and NEUTRAL and if they are exactaly the same amperage (Weight) the unit is balanced.. but if one is heavier than the other the thing trips.
However the GFCI does not care if it's 1 amp or 20 amps. it only cares if the two currents are balanced.
There are a few issues that can cause a GFCI to trip, trip, trip on a motor home or trailer, Though I've only expierenced one of them (And that in a house, I should note three of them apply to a house) I have heard from folks who had all 3
1: Faulty GFCI.. Hey, it happens (See note on a 4th optional problem)
2: Wire fault.. One poster had a hot to ground short in his rig.. That will trip a GFCI 100 percent of the time
3: Water in an outlet (This is very common and the one I've experienced)
4: Floating ground (RV on inverter or generator, SOME GFCI's are not inverter friendly. You can check with XANTREX to find a list of ones they know work,, I have a Prosine 2.0. Xantrex has tested with the following.
Leviton 6599/7-1 and 6598/722 (With polarity check and indicator light on the last one)
Eagle Shock Sentry, and GF15GY
Pass & Seymore 1591-WCN
Hubbell GF5252GYCN and GF252GYA
Bryant GFR52FTI and GFR82FTI
However I truly suspect the outdoor outlet on your rig.. Check it for cracks in the cover and evidence of water in the outlet.