We have a different model, but it's worth looking in similar locations. You have 3 slides, I have one.
The controller for our bedroom slide is under the wardrobe/pantry, just forward of the slide. To access it, I remove the 3 drawers under the wardrobe/pantry:
I reworked all the wiring in this area as it was haphazardly routed. Additionally, the wiring to the motor on the aft end of the slide was not well routed as may have become abraded by the mechanisms had I not taken action. I rerouted it a bit, and added a small cable loop to keep it out of harm's way.
Good luck, and let us know where you find the controller for your errant slide. No doubt, as you have 3 slides, you'll have 3 controllers.