Hi James, Welcome to pinside!

If the Coin unit is correctly stepping forward only one position when you set up for a two player game, this is the part of the circuit that controls whether the Player unit is stepping for a 1/2/3 or 4 player game. Most likely the Coin unit disk or wipers are dirty or there could be a broken connection.

Inspect and diagnose this circuit with Alligator clip jumper wires
http://www.planetimming.com/Pinball/troubleshooting/EM%20Troubleshooting.pdf
http://www.pinrepair.com/em/index3.htm#features

pasted_image (resized).png

I recommend diagnosing the problem before repairing it.

@MarkG's pinball repair clinic is happening on Thursday
https://pinside.com/pinball/forum/topic/an-em-pinball-online-repair-clinic/page/2#post-5708949

Or if you'd like to try a phone call, send me your cellphone number in a private message and I'll make a first reply with a text message.