Look at the switch on the drop target too. Sometimes the metal armature will be a little loose and sloppy, causing it to get hung up out of it's normal position and not allowing the drop target to fall. Could be the little tabs the armature clips to on the switch are worn or broken, which will give it too much play. Sounds like this is your problem with the drop target sometimes not going down. When it happened to mine, no matter how hard I hit the drop target, it would not go down. Would work sometimes, then get stuck and not go down. Replaced the switch, problem solved.

It's in right spot. The drop target falling is what activates the switch

make sure that metal arm doesn't have a lot of side to side play in it. If it can move too much, it will get too close to the drop target and prevent it from falling because the metal arm is stuck on the eclip or some other place on the target.

If you're hitting the black drop target with a ball and it's bouncing off because the target won't fall, something is binding it from doing so and my first suspect would be that switch arm. Short of that, the targets do get quite dirty and grimy, which can prevent them from falling smoothly. You could also take the drop target off, give it a good cleaning, and I usually rub some fine grit sand paper all in the grooves you see with the 2 eclips to make sure they are nice and smooth. Clean it all though, the posts that go through the target, the sping, washer, eclips....they can get sticky over time.