Thanks. I finally got this portion working. Turns out one of my keypads is always being seen as terminating the bus even though there's no terminating jumper. It wasn't the M1XIN, it just happened to sit after it on the M1DBH. Anything I added after that was wonky.
I ended up adding each device one at a time, moving that keypad down with each addition.
Yeah that took 12+ manhours to figure out. I kept recrimping wires, tried everything...