There's a schematic on ipdb.org.
Stardust Player Unit (resized).jpg
If the Player Unit resets but doesn't advance, start by looking at the Make/Break switch on the Player Reset relay.

/Mark

The left most switch on the Player Reset relay with the three leaves is the Make/Break switch shown on the schematic in reply #2. The normally closed or left side of that switch supplies power to the Player Unit Step Up solenoid.

What does "showing a closed circuit" mean? If the switch is closed it should read an ohm or less on a multimeter. Try cleaning the contacts on that switch with a dollar bill or piece of paper to see if that helps.

If you manually step up the Player Unit a few steps, then start a new game, does the Player Unit reset to the home position? That would tell you that the other switches in that circuit are working.

Do any of the three Bonus relays ever fire?
Stardust Gate relays (resized).jpg
The three Gate relays all rely on the yellow-blue wire coming into the Advance Unit. That same wire is used elsewhere in the Advance Unit to fire the Bonus relays as the Advance Unit steps through it's various positions. If the Bonus relays work that will help narrow down where the problem is.

The switch on the Tilt relay on the right side is another possibility, but a bunch of other stuff wouldn't work either if that switch were open.

Your DMM doesn't measure open and closed. It just measures resistance. A closed switch typically shows a resistance of an ohm or less, or about what you'd measure if you touch the probes together. An open switch can measure 10 ohms or less depending on the circuit. What the meter measures is the combined resistance of all of the paths between its probes, not just the switch. When that switch opens there is likely another path through the circuit, probably through a coil or two that the DMM is measuring.

The fact that you see a difference between the resistance of the switch when it's opened and closed is encouraging and probably what you'd expect to see. But still, unless you can measure an ohm or less with the switch closed there may be some cleaning to do.