Engraving issues

[komatias]

I cannot comment on the electornics and motor settings.
The video you posted shows repeatability which is a start. If the lost motion is repeatable it will....repeat. It does not show lost motion. Backlash in the screws or bearings tends to be repeatable and that is why in old milling machines and lathes we only cut in one direction.

You may have already done this but for the benefit of other, what I would do to ensure the screws are not moving is:

1)put the dial indicator on the captive ends of your ballscrews
2)run the gantry in one direction only for 20mm. This will take up the slack in the opposite direction of travel.
3)zero the dial indicator
4) run the gantry in the other direction and see if the dial indicator has jumped. If it does, your screws are not rigidly held in place.