I don't have the schematic, but does it have a bank? And if so, is that resetting? Something in the reset process isn't doing so, so you need to track that down. Does it have a hold relay, and if so, is that engaging?

Does the ball(s) release? If so, does it not do anything else to be ready to play, other than stop the motor?

Check these switches, esp. the two make/breaks.

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Track down each relay by its letter and the schematic, and esp. on the M/B sw. make sure they're clean and making solid contact when they're energized and not making contact when not.

Good reading, from Clay's famous guide: http://www.pinrepair.com/em/index2.htm#clean
The whole thing is worth a look when you have time.

Except for D, which is NC.

D is the reset relay. Syco, I think you may be relying too much on visual; I've had times when the contacts 'looked' like they were making good contact, but a poke with an insulated tool showed that they actually weren't. Also, make sure the switch stack screws are tight, before cleaning/adjusting contacts.

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Check the make/break on T.

Excellent! Please check as "resolved."