The slides usually have a long elastomer "blade" seal that is fixed to the wall of the RV and sits against the roof of the slide. We had problems, when we first bought our rig, that indicated that the blade seals were snagging on the slide roof and folding over.
I applied a spray-on Molybdenum dry-lube and reattached the outer corners of the seals where they were pulling away from the wall. Haven't had a leak problem since.
Frank Damp -Anacortes, WA,(DW- Eileen)
ex-pat Brits (1968) and now ex-RVers, as of 08 Dec 14.