Contacts on the 100 strips might be running off to soon.
Manually reset the unit, then manually step it up 99 times then check for continuity.
In reality the next coin (100) should run the contacts off the strips.
the 100 pay uses an outboard carriage wiper, so TGA's original description is right for that pay. When the finger falls off the 100 trace doesn't matter too much, as the C.O trace is what is completing the payout. The 100 trace just needs to get the main wipers to the C.O. trace.
typically an outboard wiper falls of the pay trace around 10-20 steps before the pay amount. Falling off at 70 would still work.
the safety timer on the 952-D is the newer style that uses the microswitch on the ratchet. That timer will shut down the game very quickly if there's an issue.
a short pay of 7 implies either the payout counter is double stepping or occasionally a step is grabbing two teeth ... assuming the main wipers are one step off the C.O trace when pay ended. If the main wipers are still on the C.O. trace, then the trace is probably cruddy or the ratchet torsion spring is too tight, the payout counter can't step up, and the safety timer kicked in per david's suggestion. If the safety timer kicks in tho, the entire game shuts down. Only light on is the red one behind the hopper.
the safety relay (thanks bally for having a safety relay and a safety delay relay) is responsible for stepping up the odds follower unit. The circuit is the same as the 952-A (schematic on
https://bingo.cdyn.com/slots/).
the circuit is basically:
1] when the payout relay first powers, the reset relay powers and keeps itself powered
2] after the first 100 pay completes, the payout relay unpowers and the safety relay powers
3] now closed safety relay switches cause the odds follower unit step-up coil to power
4] a step-up arm switch on the odds follower unit unpowers the reset relay
5] a now open reset relay switch disconnects the safety relay
6] when the cap discharges the safety relay unpowers
7] now open safety relay switch unpowers the odds follower step-up coil and the odds follwer unit steps up
8] if the odds unit is stepped up enough, the payout relay powers again for another pay and the cycle repeats.
sounds like your safety relay isn't powering, so see if the reset relay is powering and check the switches in the safety relay path.
to test the safety relay, diode and cap, play multiple coins and with no winner manually close the reset relay. The safety relay should power and [3] thru [7] of the above should happen.