Well, since I was given a heads-up on the serial port issue, my serial feeds are in groups of six. So, I can disconnect six at a time and narrow any issue down to those six leads. When I pulled the lead that was lighting the DZ-2001 LED, all the other switches worked again.
I used the CSM2 Breakout Boards for my switches, so it was pretty easy to just pull the DZ-2500 wires from the breakout board press-in connector and install the new switch machine.