Quoted from GRUMPY:
This sounds to me like you need to have a ball in the trough, a ball in a certain lock and a ball in the shooter lane. In switch test all you should see is the 3 switches that are closed by the three balls. If more then 3 switches show up or an incorrect switch shows up then you have a problem. You need the let the test go thru 2 to 3 cycles to make sure the problem doesn't show up. Also is there a ramp that can be in a certain position that causes this problem.
What I see as a tricky aspect is this has happened with both one and two balls in the lock. I don't know that any of the players have had it happen with one/two balls locked and the ball in the shooter lane. Not saying it's never happened, just not a pattern we've seen. I'm also not sure the trough is a factor either, only because it has happened with 2 balls in the lock and the third ball in play. IIRC, there are 3 balls in the game, so with 2 locked there would be nothing in the trough.
This reminds me of an issue my friend had on his Baywatch. If you hit the left flipper with a ball in the shooter lane it would plunge and fail the skill shot, instead of letting you change the skill shot selection (there are 3 options). In the switch test mode if you had a ball in the shooter lane and hit the left flipper, two other switches would register (right sling and right inlane or outlane, can't remember) and those formed 4 points of a square on the DMD. It took me hours, but I eventually found that the wires were done wrong on the shooter lane switch at one point in time. The wrong legs/diode orientation were the cause and once I fixed that everything worked great.
The difference here is that I can't seem to duplicate the issue on WW, and none of my top players have noticed a pattern to give some clues. Glass off doing all sorts of combinations of switch hits won't kickout the locks. Put the glass back on, play a handful of games, and at least once the locks will kickout with no audio or display indicator of what the game thinks is happening. The most gremliniest gremlin I've run into yet while working on pins.