I'm not a BP shooter (yet
), but one of the things I've picked up from some BP shooters that I'm gleaning info from is that sometimes the caps disintegrate and pieces fall down in front of the cylinder face. I note that you state that the caps are not "backed out," but that's not exactly the same thing (unless I just missed it). If I remember my conversation with my BP guru, the solution was to change cap brands, but I'm sure somebody else with a lot more smarts in this area will chime in.