I can not seem to find the problem with my Xenon. Any help would be greatly appreciated to solve this head-scratcher.
Basically when you have a captured ball in the lower saucer and the second ball goes into play, the first time you hit any of the four thumper bumpers with ball 2, it will eject the captured ball when it should hold it till you collect 3 more top saucers. If I manually go through the 3 saucer shots it will proceed normally and put second ball into play, but hit any thumper bumper and the captured ball flies out.
I am running an Alltek MPU with an original solenoid driver board. I've been checking switches, diodes, and any possible bad wiring, switch test shows 0 codes, and I just can't figure this out.

It only fires side saucer when ball is captures and second ball hits a thumper bumper. All solenoids fire in order during test and there are 0 stuck switches indicated.

When the ball kicks out, if I loose the ball I can still have the second in play until I loose one, and it will end that turn with the second ball still in play. It thinks it is still captured. If I can recapture the first ball again it will continue to save it until I get the third top saucer where it proceeds normally with Exit Ball routine, but if I hit another thumper bumper it will continue to fire out of lower saucer. Very odd.
If the solenoid driver board was bad would it act normal in all other conditions except during captured ball?

If I manually capture ball and then touch thumper bumper it will kick out automatically and the switch above the lower saucer has normal looking gap. It doesn't appear to be an issue with that switch tripping due to vibration/movement.

No amount of movement or hitting it will trigger it, the saucer solenoid. The only trigger I have found is during ball capture and hitting a thumper bumper (any of the 4). This machine had this issue when I bought it and got put on the back burner for awhile but now it is like a mission to make her work right. Takes all the fun away when it miss-functions.

I am not sure if it is related, but randomly usually once a game, on different switches, I get a credit award plus the extra credit crack.

My xenon has brain damage. I may have to do a solenoid driver board swap from Elektra, should be the same.

OK, I think I have that one problem rectified. it appears there was a wire at the switch that was just barely holding on, I re-soldered and tried it out and ball eject appeared normal with no kick out when thumpers were hit. So I put the glass back on at tried a new game and now it constantly resets balls. This has to be a switch issue so I will do some more testing and see if I can get past the next issue.

Thanks all for the input. There is a learning curve fixing these things. Appreciate the help, thanks.
Edit note There seems to be another wiring issue in the coin door. Not sure exactly, the problem seems to have fixed itself when I opened the door. They are fussy machines apparently. If it happens more often I will have to look into that.