I think this is just the nature of the mechanics. If we were gently raising the targets up uniformly , holding in the uppermost position until everything moved properly into place and then gently lowered back out of the way as the drop target locked in, they would always reset fine.
But what we have is a bar slamming the targets up, then quickly jerking back as the springs pull the targets down and forward. Odds are - sooner or later - one is going to miss catching on that ledge. It happens.
Tweaking, messing with the spring tension and what not, can reduce it to a point, but eventually you reach a point of diminishing returns. A target not catching once in awhile is much better than a target getting stuck halfway down.
One target not catching on every 30 resets, I could probably live with.