Ok looking at the schematics, 1 on each of the displays is segment 'h'. This is a different segment then all other numbers. Segment 'h' on player 1 to 4 is driven by gates on Z16' pins 10 and 12.  I would be fairly certain this is your fault, replace Z16 it is a 7404.

The reason the 1 works on the credit display is that segment 'h' on this display is driven by Z17.

This should fix it. If not it may be U5 the 40 pin 6532 display control, but I doubt it. Replace Z16 and report back.

You could also check pins 8 and 16 of A1 J2 but I doubt they would both be faulty. Pin 8 drives seg h for 1st and 2nd player and 16 for 3rd and 4th