Help needed! - This is a brand new issue. I noticed that all of the used switches in column 6 on my Terminator 2 machine are not working. I checked the wires to the switches and don't see any that are disconnected and all of the diodes are present. I had recently put switch covers on the respective exposed switches to hide them and I wonder if by putting them on that I pushed something together that caused a short? I see that U20 on the CPU board "controls" the switch matrix. When looking at U20 it I see that it appears to have been worked on in the past (see the pic below) based on the wire mod and what appears to be solder traces. It has, however, operated without any issue for years until now. Any thoughts on how to proceed? All help is greatly appreciated.

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