Hey Derek,
I did not understand where @eJohn measured the 69 ohms.
The method I describe here to check for shorts to rails is what I would do before measuring the coils (given the fact that the motors operate) and this method does not require to disassemble something except unplugging the stepper connectors at the controller.
Of course I would absolutely examine the flimsy connector crap that is used throughout the machine for errors – by sight also which requires disassembling. What I meant is just, what I have learned is, non-invasive diagnostic methods first, then invasive.
But considering the home losses that eJohn describes, I’m more inclined to assume fault in the area of sluggishness of the ball nut due to one of the causes linked above.
Of course, several errors can also occur at the same time for the purpose of general confusion.