My top pin position keeps dropping down a bit after every shot. I'm trying to think of the right nomenclature to use to describe my problem, but I'll describe as best I can. What's happening is that my 20 yard shot "falls" a tad bit down into the 30 pin position after each shot. Doesn't do it at the other positions, just the very top 20 yard pin position. Anybody familiar enough with it to tell what I need to tighten up to get it quit dropping? I have to reach up and reset it after about every second shot or my shots start climbing up.