Ok, I have had my Forest River fifth wheel in 4 time for slide leak. Only leaks when closed, they have replaced seals inside and out. Forest River is now saying it is the dealer, Camping World, who is...
My trailer was designed without a top flange on the two slides and would leak slightly in a hard blowing rain. As newman fulltimer suggested, I installed slide toppers and the problem was solved. The other benefits of the toppers are a plus.