Water intrusion is always a big issue that needs to be taken care of ASAP regardless if it is an RV or a house.
If you have a washer dryer in the closet I'd look closely there to see if you have a loose fitting / slow leak. If not, I'd suggest checking the windows in the master bedroom and see if perhaps some rain is getting in there and traveling via the frame to a collection point forward and below. Many units have sealant on the tops but it tends to not be all the way down the sides or bottom. Perhaps wind driven rain as well near the hitch if you've been in some storms or driving in the raid.