Looking for some ideas. When I cut extruded or cast acrylic, any thickness, the rear side gets these weird kind of craters/score lines that lead out away from the cut. I have minimized power all I can (example, the photo was done at 8mm/sec 20% (on an 80W red and black) through 10mm acrylic). The job is held up in the air on piles of magnets (sits around 30mm up) from a solid steel bed, air assist on, plenty of pull on the main air extract. There is not much “smoke” residue showing that the air flow is pretty good. The marks really are like little scores/gouges in the surface and seem to come out as little radial arcs away from the cut, almost like blast lines.
For cutting acrylic you usually don’t want much air assist. Turn it down to just a breath so it protects the lens but not much more.
those are stress lines
There are many types of acrylic, they all behave differently.
You can de-stress your acrylic before you use it by annealing.