Sounds like a flaky trough switch intermittently showing closed, making the game think it has too many balls in the trough.

I am having the exact same problem with my Grand Lizard. As you know it doesn't have an auto launch but as soon as the first ball goes out a 2nd ball gets served into the shooter lane. I recently had someone over who was looking at another machine of mine take a quick peak at the GL and found a possible issue with the 5v coming from the power supply. I have a replacement PS coming from xpin Im hoping that this may resolve the issue? I will report back my findings after the PS swap

I had this issue when I first got my DW. Run the switch test to see if, when the 3 balls are in the trough, all trough switches are consistently, properly active. I did this test using my hand but got false reads. When I used the ball my Ball 1 sw was not fully engaged and so the game thought it still hadn't kicked out a ball. Did a slight adjustment to the switch arm and problem fixed. May not be your issue but it's the first place I'd look.

Sounds like a misaligned trough switch (see what I was saying about optos at York?) - code in your machine includes auto launch for multiball, so using the lane switch it knows that another ball has been added and the machine auto-fires.

Definitely in the trough.

-Nick

I've seen many threads (including my own where SG did this) discuss auto launch issues. It always came back to the trough switches. Test, test and retest again.

Pull the glass and the apron so you have a really good look at the switches. Could be the switch is fine, but the balls are not aligned "just so" and the switch is not triggered. If it's really subtle you might need to set up a camera to record the state of the balls in the trough and the shooter lane to see the exact pattern.

faz

Yes, it would always launch two balls into play.

Man I'm glad you got it figured out. It was killin me that after that restore that you were getting this pain in the ass. Play on playa!