So I have an axis problem on the X-axis. Not sure if it is backlash / worn lead screw or a problem with the axis cable or controller. I swapped over the X/Y plugs on the controller and still got the same problem in the same cable. This leads me to think it is not the controller but either the axis leadscrew itself or the cable. Here is a picture of the part. Note that the walking back and fourth on the x-axis has happened in a thin part of the model aligned with the X-axis where it had to step quickly back and fourth over a short distance.
Here is what the part is supposed to look like for reference.
This turned out to be a classic problem with the end-stops causing interference. Disconnected the end-stop on the X-axis and the problem went away. Moving right along !
Bracket mounted on the mill ..