Hi Lambecka
in Your pin the "Bonus-Score-Relay" is made pulling - it establishes Self-Hold-Current (?) and stays pulling for a while (?) - it closes a switch to make the motor to run - it closes a switch so when the motor turns and actuates switches: Current flows and causes the Bonus-Unit to step down. All this works in Your pin.

See the JPG - the pulling of Bonus-Score-Relay must close "its switch, encircled red" - the Bonus-Zero-Relay is not yet pulling so its switch is closed*** (encircled red, brown dash) --- the Bonus Unit stepping down from position-ONE down to Zero (bonus on the unit) makes the Bonus-Zero-Relay to pull-in so its switch opens so no more Score-Motor-pulses can reach the 1000-Point-Relay.

I first would have an good lool at "my encircled red" switches - wires truely soldered-on (gently pull a bit on the wires) ? contactpoints clean ? switch gapped correct - closed when should be closed ?
IF (if, if) No luck: Investigate the connecting wires (marked orange).

closed***: From the schematics I show on the JPG (left side) - I believe the Bonus-Zero-Relay pulls when there are no bonus on the bonus unit. Greetings Rolf

0Flip-flop-pinside-Work-06 (resized).jpg