I'm cutting some 3mm acrylic on my Epilog 40w but no matter what I try it doesn't cut consistently (see attached). Some sections cut perfectly but others don't cut at all and when trying to separate the cut section it tends to break. I've tried turning the job 90 degrees as well as trying different speed/power/Hz. I ran a piece of 6mm MDF and it worked absolutely perfectly. I have tried cleaning the lenses but it still seems to only cut parts of the outline. Any help would be greatly appreciated.