rain leaking thru slide

We had a problem slide leak above the dining table in our then new 2013 Cougar 331MKS (opposite side from the stove). We took it back to the dealer several times. And, next time out in the rain (we live in the Seattle area; it rains here!), the leak was back. They said they did negative pressure checks, blamed us for not checking for cracked caulking, etc. But, every time it rained after the dealer sad they had fixed it, it leaked. So one day in the rain I looked at the slide and water seemed to pool in a certain area against the seal. So I brought the 5th wheel back to the dealer. What did they do? They said that the roof backer board was warped so they replaced the entire slide roof at no cost to us. I asked why they didn't look at that to begin with. I was told that they try cheaper options first. So, I was stuck cleaning and drying the interior several times, driving it back and forth to the dealer, and them spending time (and their money) on fixes that did not address the problem. The moral of the story: be persistent with the dealer/repair facility and research on your own if you want a positive result.