Not sure if you have a slide control module or not.
I have one that is located in my rear passenger side rear electrical bay screwed down to the floor. There are ~3 wiring harnesses plugged into it.
It is plausible that moisture could get into the harness and cause a problem.
I'd suggest trying to find your slide module and use some electraclean, pull each connector out, spray both the male & female portion, and put back together.
Worth a shot.
Other then that I have nothing.
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi