My best guess, and I am not the greatest diagnostics guy. Is the targets are resetting ok. One note you made was that you manually reset and still had the problem. Generally when you move something manually, you do push harder and hold a second longer than the coil would reset it. So that may have answered your "is it resetting completely" question.

Is it the same 2 or 3 targets? If so, best guess is that it may be the flat edge of the target that holds the target up is worn and just not catching solidly. Then any vibration, knocks it loose. That is a late evening, off the cuff best guess and could be completely wrong. But worth inspecting the targets if you can't get a better suggestion.