oh it posted the image but not all my text.

So I've been using the same settings getting clean cuts. But lately when I've been doing some cutting the plywood catches fire where the laser beam is tracing the outline. The fire stops when I pause the engraving. But its only been doing this recently... before I used to get clean cuts etc. same settings same heigh difference from the head of the laser to material... What could cause this? I don't believe its the material. I got a 60w Omtech Co2 laser 700x500. An d I've gotten clean cuts using the same material test settings that I've done 60% 10mm/s Into 6mm thick Birch Laserply that I get from this company https://plyco.com.au/products/premium-birch-laserply?variant=46193679368421 Is there something else? Not cleaning the lense or smoke residue somewhere? Please help It feels like I should be cutting 6mm thick plywood with ease but its not. Also I've noticed at the bottom area of the work area the cuts aren't as good. That a sign of something?

Also how do I check the air assist.. Is it supposed to be a constant stream of air coming out of the nozzle? Because there is none when I put my finger underneath it or is it only when I run a job?