Did you ever start a game, or just install the 3 balls and one in the shooter lane? I'm not positive but I don't believe the double lights flash during test, it is accumulative from game to game as well. I would just put 4 balls in and let them load up on their own, then try pushing start. What knuckle do you mean? On the top of the catapult "m" ramp? In order to retract it you have to hit the flipper to release it.

Yes exactally, let 4 go down the drain. When you turn it on it should search for the balls and load them.

It almost sounds like the first ball loaded doesn't make it all the way in. I'll try and look at mine later and see if I can come up with some ideas

I think that may be your problem is the first ball isn't going all the way down. Does the ball look like its right next to the shooter lane?

Does it retract during test? If so it may just be a bad switch and not registering the ball

It should be in the switch test, I'm not 100% sure, I can take a look tonight if you don't figure it out. Have the balls ready to load, and run the test to see if it kicks one to the shooter lane, that'll be an easy way to see if it is working in test