i don't know how deep you control the connections
between the switches an the keyboard-controller. Perhaps your problem is a
broken line on the keyboard matrix ?
I have an Apple ][+ that I have had for a while
and was working fine last month, now the 1,2,a,s return and space bar keys
stopped working. I checked connections from controller board to keyboard
and all are good. I checked switches on keyboard and all are good. I
reseated keyboard controller chip and still have same problem. Any help
would be great! :(