Do you have a schematic for it? I would check the entire specials circuit for that feature. Does it still award a replay for score tiers? There is likely a switch that isn't quite making proper contact in that path. Outside chance it could be a wire or connector, but I would check those switches first.

One way to locate it is to look at the illumination part of the schematic (upper left portions) There will be a bulb for the special there. Figure out what operates that bulb (will show a switch and it's relay letter) It should also have the wire color code. Once you figure that out, you're on the right track. Since there's a user selective plug (liberal/cons.) I would double check that jones plug as well to make sure it's making contact. Those prongs get a bit corroded. I use a small welder's brush ($1 @ Lowes) to clean them up if not too bad). Hope that helps. This is not a big problem, I bet we can figure it out.

Is there a series relay on the machine? If so I'd clean and check those contacts. I especially like stashyboy's suggestion about reverse-research by locating the bulb circuit. I've used that method many times.

I didn't mention I just sold my El Dorado before X-mas, or esle I would look at both the game and schematics as well. You're on the right track. It's a bit complicated, but look at the path thru that circuit and I'm sure you will see it is connected to the replay unit (in back box) and knocker when the lit spot is hit.

Thanks for explaining the fix for future reference!