@buggalugs Welcome to the group, Eddie.
It’s been years since I’ve used UGS, but here is an explanation of that error code in the gSender documentation
Error 33
Can pop up as “Motion command target is invalid” and usually comes from issues with G2 or G3 arc/curve movements in the g-code. If the target is invalid you might want to verify the file again in gSender or regenerate it in CAM with the right post processor.
For example, there have been many reports that if you use the inch post processor in Vectric, Carveco, or Fusion 360 then they won’t add enough decimal places to satisfy arc curve calculations – which will cause an Error 33. The best solution is to just use a mm post processor to get more accurate movements, or for Carveco use UGS grbl.
You may also want to ask on the UGS forum. Good luck. Please post back when you find the solution.