I think "house panel" refers to the fixed abode of the poster, not to the RV panel. It must if it controls the socket that the RV is plugged in to.
Since it's OK until the surge protector/power monitor connects, it would seem that the wiring up to that point is OK (not shorted, etc.). This would imply that the lead for the RV is not the problem. You seem to have some sort of a problem in the RV wiring itself—probably a short—somewhere after the power monitor. If so, the circuit breaker popping is quite possibly preventing it from going up in flames. The suggestion to try circuits in the RV individually is a good one for starting to track down where the problem may lie. I would tend to guess that it's close to the power inlet and distribution panel, as I would generally expect a branch circuit breaker in the RV (at 15 or 20 amp rating) to pop before the 50 amp breaker, but that's not fully guaranteed.
If you can verify that everything in the RV is safe, it would probably be worthwhile to try replacing the 50 amp breaker. Breakers have been known to wear out sometimes and cease to carry their rated load. That's not the first or second thing to suspect when one pops, though.