What I'm about to type might be stupid, coming from a person with no CNC experience, but isn't this caused by the movement being done in two steps, rather than simultaneously? so instead of moving say 1/4 step up and 1/4 step left at the same time to get an angled movement, it first does 1/4 step up and later on (scan later?) a 1/4 step left, which results in a step made in the material.

Regards,
dsc.