I had the same issue today and it took me a while to fix.
In the end to get the drop target working 100% properly in all scenarios (up/down in coil test, down when hit by ball, auto-down when a ball is behind it pushing it forward) I had to do all the stuff others mention PLUS *extend the firing pin with a piece of plastic (?!)* to fix the issue with the target not going down when a ball is behind it:

- Order a new ledge from Marco: https://www.marcospecialties.com/pinball-parts/545-6163-01 (much better than the very thin original one!)
- Order some nylon M5 washers

- Turn the power off, unplug the machine, remove lock bar, glass, balls then raise playfield
- Use a nutdriver (black screwdriver with screwdriver end removed,yes I am a noob) to remove the 4 bolts attaching the drop target mechanism to the playfield being careful not to drop it
- Unscrew the 2 screws holding the old plastic ledge
- Replace the old plastic ledge with the new one, making sure it's the right way around (it has a nice slope on it - thin end goes at drop target end)
- Put M5 washers under the plastic ledge
- Reverse the left screw so it screws in from the top (the black plastic slide was catching on it as Aurich noted)
- Put the right screw in as it was before
- Extend the firing pin that hits the target to knock it back down by adding a piece of plastic (I clipped a piece of plastic from a 3-prong plastic plug cover I had in a drawer and used it to cap the pin)
- Put the mechanism back in and reattach the 4 bolts
- Plug the machine back in and turn it on
- Open the coin door and use the menu to test the CENTER DROP TARGET UP and CENTER DROP TARGET DOWN coils - success
- Roll a ball behind the drop target and keep it there with some cloth
- Test CENTER TARGET UP and then CENTER TARGET DOWN with a ball behind it - success!
- Take the cloth out, put the balls back in, put the glass and lockbar back

Now it plays better than ever and it only took me about 8 hours to fix lol

Sorry no idea about the Pro.

8 months later and the drop target started acting up again this week (by refusing to stay up). This time I fixed it by rotating the coil that pushes it up to the left to straighten it (it seemed to have rotated to the right).

Also, the coil constantly firing to try and raise the drop target managed to shake the network cables that go to the 8 triangular lights in the middle of the playfield so they stopped lighting up. Thankfully disconnecting and then reconnecting each of those network cables fixed the lights.