Tracy,

If you go to this site, and scroll down to the bottom, you can see the connections to the front panel membrane switches.
These are not shown in the service manual schematics.

http://www.rhodeschroma.com/?id=polarisserviceschematics

If you look at switches A and G you will see that one end of each is common, and only the other end is different.
One connects to J9A-3 SWSTB4 and the other connects to J9A-4 SWSTB5. If something is shorting those two
signals together, such as a solder splash, or possibly a bit of the old membrane flex still in the connector, then when
you press G, you could get an A. A lot of other pairs of switches would also be joined by such a short. I suggest
you troubleshoot the front panel issue and get it resolved before trying to troubleshoot anything else. A DMM measuring
resistance should help to see if there is some kind of short between those two signals.

Bob