Just guessing here...Game over light should be controlled by ball count unit,which in turn is controlled,in part,to the player unit.So if it plays right on 1 play and goes game over early on 2 player it might be in the player control unit.
Check schematics to see what tuns on game over light.Might be game over relay.
The double kick means your ball eject relay(outhole) isn't dropping out early enough so the score motor double pulses it.Check points on realy and score motor.Again you will need to look at schematics and see what pulses the outhole relay.
Good luck with it