Funny story last night...
A few weeks ago I had some friends over and one of them was playing Dr Who. Twice, the ball got hung up near the Time Expander left lock. I didn't think much of it at the time.
Last night I was playing it in my dimly lit basement and I shot the Time Expander left lock. I looked down to launch the next ball into play but it never came. I looked back up and there was no ball in the left lock. "Where did it go?" It didn't get kicked out. I looked around to see if the ball got lodged somewhere. Ball search didn't find it. I look around a bit more. Then I looked at the left lock again closer. It was just a hole! The ball had hit the left lock and knocked the kicker assembly straight down into the cabinet and the ball was rolling around the bottom of the cabinet. Found both screws and reinstalled.