The machine has a red dot that is badly not collimated with the CO₂ beam:
The scorch from the CO₂ beam should be dead centered on the red dot.
It looks very much like whoever adjusted the mirrors believed the red dot was properly aligned with the CO₂ beam, got the dot nicely centered, and didn’t notice the CO₂ beam is burning the bushes.
The manuals appear entirely generic and, in particular, make no mention of the red dot collimator.
Get on the phone with whoever sold you that thing and get the doc relevant to the red dot collimator.
While you’re waiting, you can adjust the mirrors without reference to the red dot just like everybody else does. 
A previous discussion covers the gory details: