Today I cut some .2" plywood that I’ve cut many times before, though not recently. I still had it in my library though, and the cut parameters were 140/Full. When I tried it, it didn’t cut through at all. I started dropping the speed and it got all the way down to 120 before it cut through. I checked the window on the side of the head and could see a slight bit of smudge on it. I cleaned it, and presto! back to cutting at 140 again.
I was surprised it would make that much difference.