Does the endless rotating occur even if no drop targets are knocked down? I had a very similar problem with my Jumping Jack. After losing a ball, if no drop targets were downed it would kick the ball out and play correctly, but if one or more drop targets were down, the machine would endlessly cycle. I could flick the ball out by hand and it would stop running and step up to the next ball. Turned out to be the spring tab snow shoes on the bonus unit weren't exactly lined up with the rivets. I cleaned and realigned and the problem went away.