If turns out the saucer switch and the pre-saucer switch are okay you might check the trough switches especially the last position where the ball is served to the shooter from. Saw someone in here have similar saucer troubles and that switch was causing them though it didn't sound like the exact same problem.

<<I can get the saucer to eject by manually holding down the switch right before the saucer for a second or so.>>

Does that work 100% reliably? When I had a Xenon I thought that switch made the saucer ball eject instantly, not after a second or two so perhaps that switch is the issue as mentioned, and is just dirty and/or undergapped.

Independent of the eventual solution - That 01 switch should have a cap on it also so if somebody snipped it off, replace it. It would still work, but could cause it to miss some quick closures. And that's one switch you don't want to miss a closure given that it brings the game to a complete standstill.