Very long story short, I found a roller in the RV that had a nut come loose and detached itself from the slide rail. After exhaustively searching on the internets, I found it is called a "cam follower."
I see where it is missing on the rear slide of our 31FS, but the main weatherstrip is in the way of getting hand access. I'm sure I can purchase a nyloc nut for it, but not sure how the weatherstripping for the slide is attached. I don't want to rip it out, but seems like this is an important bearing/piece that needs to be on the slide.
Also, has anyone had an issue with the front slide slightly sagging toward the rear and where can you adjust it? The manual isn't very helpful.