@dpcollins - There is a YouTube channel by a SarbarMultimedia which tries to explain the VERTICAL lines in finished piece in terms of “high frequency impulse engraving.” A bit technical for most hobbyists (I don’t understand it all myself), but pretty interesting. Basically, he comes to the conclusion that it’s the stepper motors which do this in relation to the speed of the laser. https://youtu.be/mXIDwQxhX3k
Thanks for your tests. I look forward to trying them on my machine.