according to my docs, the 1046 was made for Atlantic Associates (I think that mostly means cruise ships).
the 873-ZZM was also made for AA, and used the same reel tapes, payout counter, slotted reel index discs, reel wiper contact plate wiring and glass. The only thing different on my list is the sign that could be mounted on top of the machine.
basically, they are the same machine, but there must be something different to give it a new model number.
do you have plastic molex plugs connecting the stuff in the top compartment to the cabinet?
do you have a schematic for the 1046? The paperwork for the 873-ZZM is on
http://bingo.cdyn.com/slots/your 5th line 777 pays 200 coins?
the payout counter is usually physically able to step a little more than 200 times (2 revolutions of the wipers). Games that needed to pay more than that either locked up for hand pay or did some tricks to be able to count more coins. Sounds like your game stepped the 200 times for the jackpot but the payout counter didn't reset. When the orange win happened, the wipers were on the trace for the orange win, but the unit couldn't step up enough to get off the end of the trace, so runaway pay.
if doing as David suggested shows no issues with stepping/resetting the wipers on the payout counter, there's only two switches and a plug connection in the reset coil circuit. One of the switches is the zero switch mounted near the spiral on the payout counter. Should only be open when the payout counter is reset. It's job is to prevent powering the payout counter reset coil when the counter is already reset. The switch must be closed when the payout counter is stepped up 1+ times.if you get a chance to send as many highest possible res pictures of the machine to slotpics@cdyn.com, I'll add them to the info on the web site. Definitely need a pic of the entire front of the machine, then pics of the internals.