I ran into that issue. I don’t remember what I did to fix it, but it is definitely speed/accel related. Some of the paid programs have more settings you can use to tune that out when you’re engraving in raster mode.
It was either: setting travel speed and laser speed to be the same (or at least close together)
slowing down both of the speeds quite a bit and turning the power down
You can definitely make it go away just by playing with the speed/power settings… or by using different software.