Agreed as above. My tech and spent a few hours getting the Deadworld mod to work properly. The long and the short of it is that the game has only one way of knowing how many balls are in play where the ring is concerned: How many balls went through the entrance opto (after the ramp and just before the ball drops onto the disc), and the exit opto (located where the crane drops the ball onto the playfield). I noticed that that the exit opto is not on constantly (looking for a ball to pass through), but only when the crane is in motion. Why this is I have no idea, but we were pulling our hair until we adjusted the crane travel so that the ball passed through the exit opto in the correct timing. It all came down to having the crane dialed in perfectly (oddly enough).

The game basically counts the number of balls that pass through the entrance opto, subtracts the number that pass through the exit opto (sucessfully, that is), compares THAT number against the remaining balls in the trough and comes up with the number of balls "in play" on the playfield.

If the machine didn't register one of the balls dropped into play through the exit opto, you'll get a premature end-of-ball when there's still one (or more) on the playfield.

Hope this helps!