I have mine apart right now as I'm converting it to WMS/Bally flipper mechs (waiting for a couple of parts), but it will be back together this week. If I recall correctly when the moon drops the ball a ball from the trough is immediately launched and the VUK replaces it after it runs through the subway.

Check the outhole trough -- it's pretty common for a ball to hang up and not run all the way down (e.g. you have an indication of balls 1-2-3-5 -- instead of 1-2-3-4) and if that's the case the game will not throw the new ball until it figures out what is going on (if the "missing" ball is missing long enough it will complain and throw a tech advisory as well.) There are two causes of this -- one is balls that have gotten too magnetized and stick together, but the other cause is the trough switches -- unlike Williams games which tend to use optos they're physical switches and if a ball is in there just right and the switch a bit sticky it can hang up. If that happens you should be able to see it in the trough looking down the outhole; when the VUK fires and tosses the captured ball in it would run the stuck one down the trough, the game "finds" it, and clears the fault.

Ok so my game is back up with the Williams flipper mechs in it (btw that's a VERY worthwhile mod IMHO; the feel is much better!)

When the game picks up the ball on the moon it does not release the next one until the ball is at the superVuk. It pushes the new ball then refills the trough. This makes sense, as there is no opto in the subway (so the game doesn't know the ball made it in there) and the moon sometimes fails to pick the ball up. It should know it immediately off the switches on the ramp (the ball has to cross one of them -- either the upward one or one of the two downward ones), but I can see where from a timing perspective that's problematic.

In any event my game does wait until the balls is at the leftside VUK before it kicks the new ball into play, so if yours is doing that it appears to be normal.

Actually, the callout doesn't always play. You'd think it would, but it doesn't always -- it should because there's no path out that doesn't include a switch, so the game could know, but I played probably a dozen games last night after getting the flipper retrofit completed and all my switches are working. It never kicked the next ball until the grabbed one went into the VUK.

I think, however, when I had 2.x code in my game (which was what was in there when I bought it) that it DID kick the new ball immediately. I did upgrade it to v5 code, so that might have changed the behavior.

With the older code I did have a couple of instances where I got the second ball immediately, the first one didn't get caught and when the first drained you were screwed as the ball was over.

With that said I had a bad diode on the right wireform switch for the return from the moon orbit at the time, but that shouldn't have been involved in the misses since the inlane switch is still hit and so is the wire switch on the way up the ramp, which was working properly. But it did misbehave a couple of times when I first got the game, and now with the current code it doesn't -- my guess is that Sega changed the logic so that it doesn't kick the new ball until the caught one hits the opto at the VUK, which is pretty bomb-proof logic wise since the moon and rocket ejector are the ways into the subway and the rocket ejector can't drop a ball there unless the rocket is tilted.