Same thing happened to me. Water came thru the foam insulation and tracked down into the slide controller. Slide was stuck out at a rest stop. I took the controller off and rinsed off the dirty road salt water, dried it with hair dryer (on cool), and put it back on.
Has worked fine for over a year. I did buy a replacement controller just to have but I'm still using the original one.
I raised the placement of the controller so if water does come thru the same way, it would not get in the controller.