There was a small hickup with the running of the machine, I got it all up and running before I cleaned up the playfield but when I moved it inside it wasn't resetting properly, the score motor was running.
Back out with the schematics and putting my brain into EM mode.
The machine would reset the Player1 and Player2 scores but after that the score motor just kept running and running.
Looking at the schematics below I worked it out that the Player1 and Player2 scores are reset and then there is an electrical path to Motor switch 1A through the Player1 and Player2 score reel zero switches (Z1 NC switch is open because Z1 is energised), Player3 and Player4 scores are then reset.