I’ve used Lightburn for a while on my Comgrow Z1 10W laser with good results. I just upgraded to a Comgo Z1 Pro 20W. I’m by no means an expert with my laser or LB, much more so on my 3D printers and CNC. So, when running material tests and other fill tests, I’m noticing that there is a 1MM shift on the X-axis on the return pass (X-). So, basically when moving from left to right, it burns at one position, then seems to offset by almost exactly 1mm on the pass from right to left. So, if I’m burning a 1mm vertical line, it leaves me with two 1mm lines right next to one another. I’m assuming it’s not a hardware issue, but I’m not really sure, I can’t think of what would cause that particular behavior.
What you’re seeing is likely a scanning offset. Confirm this by creating a filled square of about 20x200mm with line interval of 1mm and bidirectional scanning.
What are the results? If the lines are not aligned that demonstrates an offset.
Also draw a circle shape. Set cut to Line mode. Then burn. Do the ends of the circle meet?
If the ends of the circle don’t meet that implies mechanical backlash.
For the scanning offset, that’s going to be caused by either mechanical backlash or from an electronic delay between laser-on and motion control. If the circle test returns a mechanical issue then focus on that.
I assume that the upgraded laser module has higher mass than the previous laser module. If so, it could be stressing the mechanics of the machine more than previously.
Do a full mechanical review with particular focus on belt tension and especially that the pinion gear is properly secured to the stepper shaft.
If the circle test looks good then correct the scanning offset with the scanning offset adjustment in Edit->Device Settings.
Yours looks pretty severe, though, so I suspect a mechanical issue.
