The drop target switches should energize the 'D' relay.

A switch on the 'D' relay should activate the 'Add Bonus' coil (in conjunction with a couple score motor switches).

Another switch on the 'D' relay should activate the 'M' relay (100pt relay). (And then switches on M should advance the score reel, fire the chime, etc.)

So one thing to check is whether the 'D' relay is activating with a drop target switch closing, and then debug from there.

But does the 'D' relay energize and lock on when a drop target is hit? That's still the first thing to determine.

Ok great. So then when D energizes and locks on, a switch closing on it should activate the M relay (which is in the backbox). But to do so also requires a switch at score motor position 1A to close (this is the switch that pulses closed five times, activating M five times, and so scoring the 500 points as a result).

So the next things to check are the score motor 1A switch and the switch on D. And since the M relay is in the backbox and the score motor is on the bottom board, there will also be Jones plugs involved in the path, so those should be checked as well.

Those are the only things in the path though - just those two switches to get M activated. Score motor 1A will be the harder one to check, since it's on the bottom level of the score motor switches.

Score motor 1A...