It has returned! 🙂

New faults has appeared :

-The left magnet stays on when a game is started.
-The miniball sticks in a lane sometimes.
-One drop target does not drop correctly anymore.

Left magnet stayed on was a shorted 74LS08.
Removed, socketed and replaced.
Left magnet ok again.

Drop target that did not drop properly seems to be that half the sticker has come loose and sticks half way down.
(Bottom half loose.)

EDIT : It is now repaired, and it waits for its owner to come and collect it. 🙂