I suspect that two of the three D bulbs (not the D pop bumper bulb) are burnt out, otherwise all three should be stuck on.
There may be a short in your Space Station unit. If you desolder the 30/yellow wire from the unit the D light should go out. If it does you could check the resistances (with the game unplugged) between the solder lug where the yellow wire attaches to the unit and the four wires that go out to the ABCD lights:
A lights: 23/blue-yellow wire
B lights: 25/blue-white wire
C lights: 27/blue-orange wire
D lights: 13/red-yellow wire
First take measurements for the A lights since those seem to work. Step the stepper through all 4 positions. You should see the resistance between the yellow wire and the blue-yellow wire drop to something less than 1 ohms when the unit is in the A position. If you don't get the same results for the other three lights I'd look carefully at the step unit, wipers, solder lugs, etc.