Well, I got home, cracked open an adult beverage, and reflowed the larger MUX pins. I don't have the skills to redo the IC but I didn't see the pins move as I picked them a bit. Reinstalled and that did nothing. So I decided to safely poke and prod a bit to see if I can find what could be wrong and discovered a bit of voodoo magic. @gunrunnerjohn posted this diagram back in Jan 2021:
Thanks for this John, I was able to determine what was what with this diagram but I am confused as to what that "MUX" wire should have voltage-wise. I see it even goes to the tender, which I just had taken apart as this loco was sold to me with some battery-related rust issues so it is possible I missed a wire in the tender.
I'm close to finding the issue just need a boost from my fellow train family.
Thanks!