I have a confession to make. I created the state PCB for TMD-3 directly in the KiCad PCB editor without creating a schematic first. This is pretty easy to do. Of course I had to turn off DRC to accomplish thus but hey I figured I was saving myself some time. Wrong.  

I missed introducing a small trace when converting the bus connectors to standard .1 inch headers and inadvertently crossed the S2 and S3 lines. Took me a while to find the problem that a netlist and DRC would have probably caught.

Fortunately the boards could be salvaged with a delicate but doable trace cut.

Lesson learned.