The wiper is just that, a wiper, NOT the seal when retracted, NOT the seal when extended, BUT NO WIPER/ LOOSE WIPER would DUMP a BUNCH of water INSIDE if retracted during rain. It is ALSO a RAIN DEFLECTOR WHEN OPEN/ EXPOSED. My 1999 Class-C with Hydraulic slides, uses a double D wiper that pushes onto a metal trim; had to adjust mine after buying in 2017; Suggest with slide fully extended, study underneath and see if you see adjustment slots and can tell if anything has moved? I was able to adjust mine w/ a jack and cut 2x4s, (support, loosen bolts at adjustment points, jack/adjust as needed and tighten down); (Luck to ya) If you do need new seals= (ABOUT $5/ LF ($200+/40-FT ROLL)
https://www.steelerubber.com/
Or
https://www.amazon.com/AP-Products-0...2093054&sr=8-5