Hi
I had a similar problem with a Seeburg sc1 where I only had 20 selections, the number buttons made no difference, my sc1 had arrived with no credit unit.
After studying the wiring diagram, I found that on the sc1 the number selections go through a set of contacts in the credit unit as mine was missing the circuit was incomplete putting a jumper wire in the credit unit multi socket completed the circuit and re astablished the number selections.
Dont know if a 3wa is wired in a similar way?
is there a plug on your credit unit? Some do & some are hard wired.
may be worth cleaning any contacts on the credit unit if you have one?
Cheers Scudie