We had a similar issue. We also have a keystone. Keystone also went through several doors with no successful result. Luckily the trailer was still under warranty and we said that we would not accept it until it was fixed. Anyways, the dealer came up with a solution (we also thought the same thing about caulk). They used a 2 - 3 inch rubber seal that went all the way around the inside of the storage door. That solved the problem and it looked very nice. It was a rubber seal that had a lip for the door and wall to fit into.