I'd bet you're right ... the payout counter is not stepping up. Ya can turn the game off and look after a few too many coins are ejected. If the payout counter is still reset, you've got runaway payout.
the circuit is more-or-less:
1] low payout relay SPDT switch - verify green/red (middle blade) wire connects to slate-black wire when low payout relay powered
2] green/red wire from above goes to cam 3 switch to make the step-up pulses. Mating switch blade wire is green/black.
3] the green/black wire goes to a payout counter step-up coil lug.
there're plug connections in the path also.
if you don't have a schematic, there's huge ones on
https://bingo.cdyn.com/slots/triple%20bell%20%28console%20slot%29/ (like 500MB and 700MB huge). One of these days I'll clean them up and get the file size down to 10MB or so ... the pacific pinball museum got a pile of schematics recently and there may be a better triple bell in there - I'll see what I can find this weekend.