Lots of possibilities...
- The GFCI in the RV could be malfunctioning or otherwise need replacement.
- There could in theory be a neutral to neutral fault in the RV that's rightly causing the RV GFCI to pop but not causing a fault to trigger the house GFCI. That's not very likely, but it is a theoretical possibility.
- There could be an actual fault and the RV GFCI for whatever reason is just a bit more sensitive or faster to pop.
- The house GFCI could be miswired or broken and not providing ground fault protection. Have you tried its test button lately? Does the outlet remain powered when it's tripped (which indicates that its line and load connections are swapped)?
All that said, replacing the RV GFCI is not an unreasonable first stab at solving the problem if everything else seems kosher.