If your Bonus Unit takes 5 steps at a time between pauses on the double bonus you need to figure out why. Here is the circuit again.
Big Indian Double Bonus 3 (resized).jpg
There are three different paths that can drive the Bonus Unit subtract solenoid. They all start with the Score Motor 1A switch on the right which generates 5 pulses per 1/3 turn of the Score Motor as shown in the Motor Sequence Chart. Only one of the three paths should be used at any given time.
The bottom path used only during reset goes through the SB2 switch and allows all 5 pulses to reach the subtract solenoid.
The middle path through the normally closed part of the make/break switch on the LB relay and a switch on the Q relay is used when a single bonus should be awarded. It also allows all 5 pulses from the 1A switch to reach the subtract solenoid.
The top path goes through the normally open part of the make/break switch on the LB relay and a switch on the Q relay and is used when a double bonus should be awarded. The Motor 2C and 3C switches allow only the 2nd and 5th pulses from the 1A switch to reach the subtract solenoid. The other three pulses are blocked.
The theory is that somehow all 5 pulses are getting to the subtract solenoid from the 1A switch when the double bonus is being counted and only the top path should be used. If that's the case the pulses are likely getting through one or the lower two paths. Either the SB2 or LB switches aren't opening correctly, or their solder tabs or wires are touching or there is some other kind of electrical path through them. It's also possible that the 2C or 3C switch is stuck closed or shorted which would allow all the pulses through. You'll have to inspect things carefully and experiment by blocking some switches to see if you can figure out how the extra pulses are getting through.