As we were putting our main slide out yesterday, we heard a large "thunk" sound and went out to check what it could be once we realized it wasn't inside. It turns out the slide topper had broken loose and was just laying on top of the slide. After getting the ladder out we did a closer inspection and found the rear cap screw (only one is used to hold it into place) had sheared off and the front one had backed out and fallen to the ground.
So I got my drill and drilled out the broken screw and then we set about putting the slide topper back on. I had to find another screw of the same size and thread and fortunately had one on board. I got out some Loctite and we put the slide topper back in place.
Lesson learned - as part of regular maintenance, check ALL screws and bolts holding things in place. We have experienced some high winds and rough roads, so it isn't surprising that things are rattling loose. We have been diligent about putting screws and bolts back with either a dab of glue or Loctite to help them hold better.