Delamination is the biggest problem with RV's. I would look at the gutter drain area as I had a similar issue that was caused by the water draining off the roof and the underside seam from the overhang where the gutters ran down the side of the camper was where the leak was. It cost a lot of money to fix and this keeps the RV industry in business fixing these issues. I can't understand why they aren't able to come up with a better method to seal these things. If I had known all this BEFORE I bought a Camper I would have bought a van or something else.