Tyler, is that the lined heatshrink with the meltable inner layer? I’ve used such in the past too.
Early in the Nomad story, when there were random glitches in the movement, for troubleshooting I took the Arduino board out of the loop and controlled the stepper drivers directly through a parallel port on my PC (step and direction). Those forum photos are long gone but I found a couple on my PC
I don’t think that’s quite what you are doing, but the Frankensteined arrangement itself didn’t introduce any wonkiness–the glitches were in the detail design of the stepper driver board itself…