BPS issue
Just a thought. Sticky extraction usually means a dirty chamber. I don't mean dirty in the usual way. Brownings can develop a fine layer of rust and plastic that is often invisible to the human eye in their chambers. Auto 5's are famous for this. Take a 12 gauge bore brush, wrap a slight layer of super fine steel wool around the brush and soak it with Hoppes or some other solvent. With the brush on a portion of rod put it in a hand drill and polish the chamber for about 3 to 5 minutes. Do this with the barrel off of the gun of course. No actual material will be removed just the hard to see debris. When the outer area of the breach starts to feel warm you are close. I have done this with Express 870 Remingtons (often just a poorly polished factory job) and my own Auto 5's and Ithaca 37's. I bet you it will work for your BPS.
cheers Darryl