I remember just went found in catalogue and ordered with a couple of spare nuts to make my own anti-backlash nut. Will photo if picture required as not happy with Tom Senior nut location.
The Mach3 version number is R3.043.062 this is run on a dedicated computer using windows 7. The first picture is of my spare board, I am not sure of the number of the board I am using but it is top left on the second picture.
Hi that is the same board I am running Mach3 on, I brought a https://www.cnc4you.co.uk/UC100-USB-Motion-Controller and it works great. Suggest you fit some Oldham couplers as well.
I had the same problem as you and replace the pot and changed the the Timing pulley and belt fitted to the pedal as it had harden and was not that flexible,works fine now.
Keep the tool a little high so when cutting it comes down to center height and usually part off at a high speed, flooding and retracting tool so the blade stays cool and does not bind.