Half tone steps are not even

I had a try using Jason Dorie’s Halftoner app lines option today, as I’d read it was faster than the dots option (it was very much faster). However, as you can see in the images the lines were not spaced evenly. The passes that move towards the home corner seem to be slightly too far over so the next pass moving away from the home corner actually touches the previous pass. I noticed this part way through the test run, and it appears to be consistent all the way through the carve.
I am in the process of trying to set things up i.e. calibrate everything properly but I would appreciate any tips as to where this issue might be.
It’s cut on melamine with a 60 degree bit at 1270 mm a minute feed rate. It’s not painted, it was a test run.
I realize the right side is not cut deeply enough, but I am saving leveling the waste board until everything else is adjusted properly.