The Make/Break switch on the FS relay mini stepper alternates between the two lights in a 5 ball game but the Sequence Completed switches also need to close:
Big Hit Special lights (resized).jpg
They might be located on the drop target banks.

You can temporarily bypass the FS relay switch altogether by putting the game in 3 ball mode and attaching an alligator clip test lead to the orange-green or orange+green wire on one side of the Make/Break switch and the black-yellow wire (not labeled above) between the FS relay switch and the Motor 1C switch. Then you can experiment to see when/whether the Sequence Completed switches are working.

/Mark

The FS relay is also called the 10-90 Unit relay and typically advances each time the N/10 point relay fires. The Big Hit schematic however shows something else (original schematic in black, my revisions in red):
Big Hit FS relay (resized).jpg
It shows that the FS relay is wired instead to a red wire between an AX relay switch and the One Runs unit Runout switch. This doesn't make sense to me and I suspect that that is a typo. I would expect the FS relay to be wired instead as shown in red to the green-red wire driven by a switch on the N/10 point relay.

Perhaps you could double check the wire colors on your game and clarify how the FS relay coil is wired.

In any event, the FS relay should be pulsed regularly during the game and should switch the special lights each time it advances. If you watch your FS relay carefully while manually scoring 10 points (or whatever drives the FS relay) do you see it cleanly advancing from one position to the next, or does it struggle, fail to advance and/or perhaps straddle two contact pads with its wiper?

Hmm. That doesn't seem to match the schematic either. What color wires are soldered to the FS relay coil solder lugs? One is probably black. What color is the other one? Is it red as shown or perhaps yellow-red?

Thanks for checking. Initially I didn't understand how that was supposed to work because the AX relay switch is only closed during reset so at first glance it appeared that the FS relay wouldn't fire during a game. However I see now that the FS relay can fire when the 1 Runs Unit Runout switch is closed which means that it should fire whenever a run is scored except when the 1 Runs Unit shows a zero. I don't recall seeing that arrangement before.

If your FS relay doesn't fire most of the time when a run scores you should determine whether it tries to fire (meaning it's getting a pulse) and fails to advance or whether it's not getting a pulse at all. If your FS relay is dirty or maladjusted it could be a mechanical issue rather than an electrical issue.

The schematic shows that the Double, Triple, 2 Home Run and 2 pop bumper lights are always on except for a brief moment while the Score Motor turns.