Just received these products and am attempting to revive Robert Washburn's old TAIG CNC mill.

2 axis work well. One axis does not. Might not start, may start if the knob is given a spin. May act as if there is no power after it stops jogging. That is, the knob can be spun as if it were powered down. Not so with the other axis.

Shinano Kenshi size 23 steppers of roughtly 200 Oz-In. torque.

I swapped X & Y steppers and their connection to the control box with the same results. The problem followed the stepper.

Cable looks to be intact but I'd like to take the rear cover off the stepper to check the cable all the way inside. Will I cause problems with this minimal opening of the stepper?

These steppers appear to like 1/2-stepping better than using 4 or more microsteps based only on the sounds I'm hearing. I haven't started using measuring equipment to really test what is going on.