I'd thoroughly clean and adjust all the contacts on the 1st player 100K relay. There is only one switch in the 1st player 100K lamp circuit, so it sounds like that switch isn't closing properly during gameplay...

Hi John
I look into the ipdb-schema - a strange thing ...
Schema-B-16 / C-16 shows Your "buzzer", Bally calls it "Horn" - a rare type of coil - it is driven by 6VAC. It is activated by the pulling (and then let-go) of "over the top DELAY relay". And this relay is shown at schema-F-20. A funny invention of Bally - for proper work: This relay has a bulb mounted - a 455 FLASHER BULB --- if this bulb is dead: Relay does not work proper. If Somebody has put a "normal (non flashing) bulb" into the socket: Relay does not work proper.

So first questions: Is there a 455 bulb mounted ? - does it light up and stay illuminated for about one second ? In the area G, H, J / 20, 21, 22 the activating of the Over the top DELAY Relay:
All four Score-Drums (one on each player) "10'000 to 90'000 Units" have an EOS-Switch - a rare "Make and Make switch": A blade is moved and closes to a second blade - they are moved further and close to a third blade = ALL 3 blades have contact.
And when such a Score-Drum is in 9th position: Another switch is closed.
When these two switches are closed: the appropriate 100'000-point-relay pulls-in. And just before it pulls-in: Through a still closed switch on the relay -> Over the top relay is activated -> and its 455-bulb when turning off by heating up: Cuts Self-Hold-circuitry of the relay -> Horn let go).

So I would study this area in the schema and have a look at switches and relays mentioned. Greetings Rolf