[folivier]

Couple thoughts, do you have slide topper awnings? If so look at the side seam of the slide on the outside to make sure the skin hasn't pulled away from the side. On my '98 the spring on the awning over the bedroom slide got stuck and pulled the skin away just enough to create a leak.
Also when the slide is open make sure you can't see any daylight around the rubber bladder seal. There is a possibility of leaks around the corners.
Good luck