We had to close in a couple openings below the bedroom slide so the cat could not get inside where the mechanism is. Check carefully for any openings both when closed up and when open. It was an easy fix. We also put a pillow in the front part of the slide so the cat cannot climb up on top of the slide when it is in.
Our cat has learned how to open the slide in the screen door and then to push down on the latch to open the screen door. We are still looking for a locking device which will stop him from opening the screen door. So far its been fun watching him do it with friends coming to watch him, but we need a permanent solution.