Inductive loads cause ghost trips. Dedicated RV outlets are not GFCI protected, the outlets in the RV that need GFCI should be on there own. Heater elements and charge converters can do this, even though progressive dynamics says it 'should be ok'. I presume you have a gfci in the camper, so now you have 2 on the same circuit and that can also cause ghost trips. Our house is an old build and had a GCFI breaker, and later someone added one in the bathroom. The breaker tripped randomly, after the breaker was removed and the gfci placed correctly in the circuit it's been fine.