Wow, thanks to Dominik and everyone for all the great suggestions.
I temporarily moved my pc close to the Xcarve then using a short USB cable I ran the same cut ( which had previously failed 4 times) and it worked ! But of course being a pessimist, I reconnected the long active cable and ran it again exactly the same except for no bit and that also worked. Don’t you just love intermittent problems. So I’ll just have to wait till it fails again.
One setting that I have changed, after the successful carve so I can’t prove it was the problem, is the COM port number ( from 6 to 2 ) and the speed (from 9600 to 115200). To do this, go to the Device Manager under Ports - USB Serial Port. Change under PORT settings. Your controller must be connected in order to see this.
Also in Device Manger if you change the View to ‘Devices by Container’ you can see the X-controller listed with the USB Serial Converter and the USB serial port . My drivers were all up to date and the power management settings were correct so no help there for me.
I’ll probably order a powered USB hub from Amazon today as it will eliminate the cable issue completely.