Probably one of the most common issues of class c rv's. We brought ours out of indoor storage and after giving it a good cleaning my wife noticed the bottom of the mattress ( leather ) has a few mold stains. After a good look, as in a 3 hour thunderstorm, we found where the water was collecting so yesterday I was off to the rv store and bought the supplies needed. Resealed the roof seams and one of the windows. It was getting late and felt a few drops and the sealant tube was empty so I figured I would finish it today. So here we go, it's been raining all day and the side with the resealed window is all dry. Just have to wait for a a few days of sun to dry it out and finish what I started.