On my 1964 'Mustang' game, the 5th ball plays and then when the ball drains, the game keeps running. It does not show 'game over' or 'ball 5' on the back light. It does not release another ball. I have to manually reach in the coin box and hit the trough switch to get it to 'game over' and to shut off the game. This only happens on a 1 player game. On a 2 player game, the game ends correctly.
(I don't think it matters, but I do have a coil coming for the lock relay because it overheats, but I would think that can't be the issue with this.)