At the start of a game, all target banks reset
At the start of a ball, all target banks reset
This is part of the normal "reset" routine.
During play, the target banks are reset only when the associated switches detect the fall of the target. So one of the targets is not being detected.
What you can do is remove the glass, start a game and then manually drop each target - watch that each target scores. The target that does not score when dropped will be the problem.
