We may not be seeing the same thing, but the lines I see in the image above will naturally be darker with darker colors because the laser power is greater. Regardless, the issue is a mechanical one of some kind, and most likely is an axis miss-positioning error. I suggest you engrave a solid black square, about two inches by two inches, at 50% power, and with .025" pixel resolution at 45°, horizontal, and vertical angles. The engraved lines should be perfectly straight in each engraving, and evenly spaced from each other across the complete square. Not being able to see the mechanical components of your machine I can not be more precise in what to look for, but I suspect the lines are caused by something like a non-concentric pulley on one of the drive belts. One other thought is that your microstep setting may be too large. It should be at least 8 to 16.