[theRat]

Sorry I believe you are wrong for the case of the VFD cable. This is definitely case for signal cables, but if you you google "vfd cable installation guide" you will get multiple results from vfd cable manufacturers and every one that I have read says the shield must be terminated at both ends. This link for example has the earthing requirements set out on the very first page.
https://www.lutze.com/downloads/file...ze-vfd-cables/

[cncmakers001]

I have a Windows 10, Dell Optiplex 9020. While cutting I keep getting the Controller Disconnected Error. SW: 2020.03.14. HW: 2020.03.12.

Device listed in windows is: CNC USB Controller Mk3 v2. Which is what I have. Driver date is 9-22-2016 ver. 1.0.0.1

I have replaced the USB cable with no change. I have tried every USB port on the front an back of the PC, there are 10. I have routed the usb cable away from all other wiring. No change. Yesterday I cut all day and it happened 3 times. Today it has happened so often I've given up cutting.

I could use some guidance. Thanks

Maybe try another PC, if another PC is working, then the problem should come from this Dell Optiplex 9020