[mactec54]

Thanks again for the guidance.
My spindle does indeed have a 4-pin plug so i should be able to ground the shield when swap out the wiring for shielded (I have some 16/4 on the way, and i'll probably pick up some wire duct and a ground block).. I'll get the signal lines separated from motor supply, mains power and 24v, and get the ac away from signal.

I forgot to check the USB ground. I'll take a look next time I'm out in the shop.

Remove any paint when you mount the Bus Grounding bar then the Box will be Bonded to with the Ground connections

You don't Ground the shield to the 4th pin that is for the Ground wire, the shield you Ground to the body of the plug like roll it back over the cable and clamp it with the cable restraint you may need some copper tape to wrap around the shield and then clamp it trim everything clean, these plugs are difficult to work with as they are not designed for shielded cable use so you have to improvise

Check the continuity of the 4th pin to the spindle body if it is not connected which most are not then you will have to connect it inside the top cap