I fixed a multi ball issue with a TZ last week for a fellow who bought a game from Greg (unbelievable restoration, the thing looks factory fresh).
The game played perfectly when we tried it at Greg's place, but when the new owner got it home he found that once multi ball commenced, the machine would not return any balls that entered the under playfield area (and would normally be returned from the slot machine).
Greg's place to Ocean Grove was a two hour drive. When I got down there last weekend, I took off the apron as I was convinced it must be a faulty trough switch. Solved the issue in a minute - slightly bent first switch trigger wire. It was pressing against the ball serve arm, and staying down. Checking it from below to trigger (as I had had him do over the phone) it had shown it working, but that was masking the issue as it was not what the ball was really doing.
When I though about it, I decided that the issue was that the wire had bent, I suspect from the ball in that spot jiggling in a non-normal way up and down on that switch for the 2 hour drive.
Lesson learned - balls out for transport.
