This is probably not a common problem on Judge Dredd, but I thought I would just post this "trick" here for reference.
Occasionally when I was playing my Judge Dredd machine (perhaps 1 in 30 games) the ball would enter the subway and get stuck in the small gap between the metal enclosure and the plastic ramp. Sometimes I could shake the machine enough to dislodge the ball without tilting, other times I had to tilt the machine and sometimes (rarely) I needed to remove the glass and dislodge the ball manually. At first I thought the machine was not levelled correctly, but after checking and adjusting the levels the problem did not disappear. I then thought perhaps the ball was getting caught on the switch inside the plastic ramp, but on close inspection I found this was not the case. Another thing I checked was that the metal enclosure and the plastic ramp were both installed correctly and had not moved during gameplay. The plastic ramp is secured to the playfield by 2 screws (if it was installed incorrectly the screws would not line up with the holes) and the metal box is connected to the playfield and to the drop target assembly (so again an incorrect installation would misalign the connections). Therefore, I came to the conclusion that the "gap" between the metal enclosure and the plastic ramp was there by design, possibly only on my machine since I had never heard of other people suffering from the same problem.
So what to do? #$#
I decided to build a "bridge" between the metal enclosure and the plastic ramp, so that the ball would clear the gap and roll down the plastic ramp to the kicker. I cut a piece of metal to size and secured it in the metal enclosure with an overhang to bridge the gap and rest snugly on the plastic ramp (see pics before and after). The piece of metal is on a slight angle which forces the ball to roll down to the plastic ramp, then the momentum causes the ball to roll down the plastic ramp to the kicker (instead of getting stuck as it did previously). I have not had a problem since
Matthew