Rockola 414 selector problem

Rainy season in the Pacific North Wet has begone so its time to tinker with the jukeboxes again.
I started on a Rockola 414 for my son's Christmas present, he requested a small jukebox for his home and it was the smallest I had. Gripper mech was frozen and its associated motor was weak, the selection motor was frozen, multiple contacts were out of adjustment or not making contact.....this was a forgotten and neglected little machine. Though I have repaired or replace the above mentioned problems, I ran into one that I can not figure out and I do have the manual but it does not have a trouble shooting section, so I need some help please.
Coins and credit buttons will register credits and the lock bar solenoid energizes holding the selection buttons and it will go through the write in and read out sequence correctly when the number button is pressed first and then the letter button. However, If the letter button is pressed first the write in sequence will start w/o pressing a number button. It will select the number "0" by default. The remainder of the selection and play sequence will operate correctly except for that selection operation. I have removed the selector mechanism and the 0 button is not stuck and operates smoothly. Ideas and suggestions are always appreciated.
Thank you, Craig.

Hi Craig,
It would seem to me, that there should be a "start/holding" switch connected to each bank of switches--so, I would assume, that the one for the number section is "stuck/shorted-always closed" ? Ron Rich

Hi
also i know its a bit of a pain but its worth removing the keyboard and washing in an ammonia solution and rinsing off well, i got this advice here and solved a lot of keyboard selection problems with a 414 and 445 i have. While its out check the wires that are soldered to the keyboard
clones

If washing it--REMOVE any "solenoids" first !! Ron Rich

Thanks guys, sorry it's taken so long to get back to the board, but had a furnace and truck issue that has been taking up my time and have been unable to get back to the juke until today.
Ron, I had checked the run/hold switches and they are both open until the key is depressed. During the scenario I mentioned, I don't get a chance to press the number switch before the selection locks in to an apparent default "0" and the number run/hold switch is still in the open position when the sequence starts. I too suspected a short, but I'm unable to locate one. I have removed the selection assembly and viewed via magnification the contact area of the "0" and other contacts but found nothing that would indicate something is shorting across the contacts prior to the normal contact during the pressing of the button. I also checked all the jumper wires that are part of the selector but run on its exterior to see if they were chaffed and making contact plus the other wires that I could access outside the protective wire casing, but could find no problems there either. I have a parts machine, so I removed the selector from that machine and hooked it up to the project machine and the replacement selector worked fine. I would still love to figure out what is going wrong with the problem selector. It would make a good learning experience and I can put it back in my parts inventory, if its not too much of a pain.
Clones, I will try the ammonia wash and see if that solves the problem. Ron, I will remove the solenoid first.
I really appreciate the help and thanks again, Craig.