The wall covering on most coaches is usually a very thin veneer plywood with a vinyl decorative vinyl surface. Any moisture that gets on the outside surface of the wall is prevented from getting into the plywood. Unfortunately any water that leaks into the inside plywood side is not able to get out through the vinyl so it usually forms little bubbles, or other indications that the plywood is deteriorating. It would be a good idea to have things examined more closely to see if things can be taken care of before they get too bad.