I'd recommend just cleaning suspected switches one or two at a time until you get things running well.

If your Outhole relay is firing and everything else is working there are really just two switches you need to investigate for the Ball Release:
Lucky Ace ball release (resized).jpg
One is a Make/Break switch on the Outole relay and the other is the bottom switch on the #4 Score Motor Cam switch stack.

/Mark

When the ball drains the Bonus Count should happen first. Once the Bonus has finished counting the Outhole relay should fire on the Motor 6B switch. Once fired the Outhole relay will keep the Score Motor running until it relaxes. Motor 6B is at the end of the Score Motor sequence so the Outhole relay will keep the Score Motor running into the next cycle. The Ball Count should fire on Motor 2A as you mentioned, early in the next Score Motor cycle. Soon after that the Ball Release fires at Motor 4A as shown in the schematic above. After that the Outhole relay should relax when Motor 5B Make/Break switch opens. The Score Motor should stop soon after that.

To slow things down you can unplug the Score Motor service jack and turn the motor by hand to watch the order of things.