Hi Jansa, I had a similar result when I was cutting cast acrylic, anything over 30% either was the same depth or less up to 80%. I was cutting through 3 mm acrylic at 80% (15mA) @ 5 mm/s and then a few days later it couldn’t do it even after three passes. I found that my back mirror in the tube had burnt. If you have a milli-amp meter make sure you are not going over 15mA.
Also, your focus doesn’t look right.
