Also, you can check out Clay's EM Pin Repair guides:

http://www.pinrepair.com/em/index.htm

You might want to troubleshoot the replay/start button issue first. Check the replay/start button switch circuit on the schematic. Make sure credits are showing on the credit wheel. Check the following relays and switches to see if they're clean and adjusted properly:

V relay
ZB relay
PB4 relay
W relay
Replay button switch
Zero position "Replay" unit switch - brown/white wire and green/white wire

I was working on a Far Out last summer and it had similar problems, which I had a hard time solving. It ended up that one of the score motor switch fingers had slipped off the score motor disc. This resulted in a group of switches on the score motor that weren't opening and closing properly. With the power off, turn the score motor manually and visually inspect the switches to make sure they are clean and operating properly...

Power is sent to the XB relay coil via the player unit. Make sure the player unit is advancing properly. You can turn off the power and then manually advance the player unit to see if it smoothly clicks into each position.

The ball return switch sends power to the O relay. The O relay switches would close to send power to the XB relay coil and the ball return solenoid.

When the ball goes into the outhole after ball 4, is the O relay being energized?