Hi Guys, Ive got a Xenon as well, and its been playing beautiful for years, a little while back it started to do the old two balls in the shooter lane
as mentioned in this thread, i cleaned switch contacts on switches 08 and 02 it would play ok for a while then start the two ball thing again,
i remember this thread from along time ago and tried some of the tips from other members.
the switch test checked out ok as well.
I finally found the problem, i took off the apron and watched the balls doing there thing, the 2nd ball would just go straight through to the shooter lane
and join the other ball that was already sitting there waiting to be plunged.
so i started activating switches with my finger, first switch 28 then hold down switch 02 where the ball should wait, the kicker did not attempt to kick out the second ball (my finger),
but when putting the ball through it would play up.
turns out that the ball was activating both switches 28 and 02 at the same time, when adjusting the switches properly the problem was solved.
on my machine there is a very fine line between switch 28 turning off and switch 02 switching on.
Hope this may help someone in the future.

Ian

 That's been my experience with those 2 switches as well. Very fine line adjusting them just right. Fortunately my Xenon hasn't missed a beat in years now......wish I could say the same about some of my other games!