Quoted from Aurich:I had this problem, or a similar one, and it wasn't an opto or switch or anything, was purely mechanical. The screw on the drop target that's on the same side as the spring was pushing it so it wouldn't latch properly. Weird behavior like phantom hits, popping up and down rapidly etc. Sound familiar?
My solution was to take out the screw on the spring side, and feed it back in from the other side, so the head wasn't interfering anymore. It won't "bite" anymore, threads won't catch on the plastic, but the other screw holds it in place, so it work fine.
Ever since I made this fix (Rarehero gets the tip for this being the problem, I think he found a smaller screw head though) I haven't had a single repeat of the issue.
Yup, this is most likely the issue, not the opto. The target is getting pushed by the screw head. I found a screw with a slightly smaller head and haven't had the problem since replacing the stock screw with it.