My bell stop was adjusted too far in. That caused the bell stop to stop the slide and it would bind occasionally. He told me to let the slide frame be the main stop and the bell stop should be secondary. The bell stop will flex the frame wall on contact about 1/4 inch when fully retracted when it is adjusted correctly. Before I adjusted it the Bell stop would flex the frame about 1/3 inch causing the bind.
It's not an exact adjustment, more like trail and error. If the bell stop is contacting the frame too early and causing the slide to bind then it needs to be backed off a little at a time until it works.
The adjustment is just the opposite of what I thought it would be but it's working now.
Disclamer: Use this procedure at your own risk, it may not work on all slides.
2011 Rockwood 8285WS
2012 F150 SuperCrew Ecoboost HD payload
Curt 20K Q5 Slider Hitch