Hi knockerlover +
I looked up in the schematic "Royal Flush" --- the snippet that oldpins shows in post-3 shows it exactly (with colors of wires). NONE of the lights work - see the "Switch on E-Bonus-Score-Relay"
with wire-color-white-black, wire-color-blue-black ?
The E-Relay does pull-in (and You are rewarded with Bonus) --- but, question: Does this Switch "truely" closes ?
The list of relays in the schematics tells us "E-Relay 5A (zero B, zero C)" - means 5 Normally-Open switches on the relay (zero Normally-Closed switches, zero Make-and-Brake switches).

Want to investigate on that switch ? Switch REALLY closes ? Contact-points clean ? wires truly soldered-on ? Maybe we are lucky - maybe we must make further investigations using a Jumper-Wire. Greetings Rolf

Hi knockerlover
great, "2,3,4 thousands" light up. I have not yet seen the inside of a Royal Flush. Here an idea - want to try ?

Look at oldpins JPG (post-3). Side by side are the wires soldered-on (at a bakelite plate on the unit). So "A-0-Mar-1000-Light", "B-1-Mar-Wh-2000-Light", "C-2-Mar-mingled-with-White-3000-Light", "D-3-Mar-Or-4000-Light", "E-4-Mar-mingled-with-Yellow-5000-Light".

My idea (can't remember having done once): With a short Jumper-Wire make a permanent connection*** "B-1-Mar-Wh-2000-Light" to "E-4-Mar-mingled-with-Yellow-5000-Light" (((You just jumper "feeding the lights"))). Questions:
When "B" lights-up --- does "E" light up ?
When "E" should light-up --- DOES "B" lights-up ?

(((May want to try on WORKING stuff - jumpering "B" and "D" --- to prove my theory right-or-wrong (?) )))

With this jumpering we test "is the fault in the stepper unit OR is the fault in the wiring to the lights ?". I do not know - please tell me: "Where is the stepper unit mounted" ? IF (if) it is NOT on the playfield: A Jones-Plug can be faulty.

connection***: Clip-on the gator-clip "one side of the Jumper-Wire" at Solder-Lug "B", clip-on the other end / gator-clip at Solder-Lug "E". When You do not have a Jumper-Wire having gator-clips: Simply wrap the bare end of a wire around the Solder-Lug. Greetings Rolf