Carrying a bike on the back of a RV in the rain for hours? in a continous heavy? water spray can cause electrical issues and shorts.
It´s like taking the bike to a steam bath. Probably not a good idea either.
To prevent those things, you might cover the bike for transportation in rain a bit. And additionally to that you should grease all electrical connectors with saltwaterresistant marine grease (the white one - not the black one for bearings). And use it generously inside and outside of the connectors.
Underneath the handle bar cover, underneath the front cover, underneath the seat bucket, just everywhere...
But the short can have other causes too. Check the routing of the wires, hoses and harnesses and check for damaged insulations.