Several years ago, we took our brand new Basecamp on its first outing. During a rainstorm, we noticed that several little drips of water occurred on the wall. Obviously, everything was not completely sealed. I went to Airstream Forum and found a post that was particularly interesting, especially after reading what all had to be done to reseal properly (according to Airstream). This person on the Forum shared that he had discovered "Capt, Tolley's Creeping Crack Cure," and that his leak problems had been solved.
We purchased Capt. Tolley's and set about going along each panel on the outside of the Basecamp. We had no more leaks. It was easy to use and solved our problem. Read about it at the link Capt. Tolley's Creeping Crack Cure