The incision changes over time

From what I’ve seen, the kerf usually only changes when the focus or material changes. Not all types of wood have the same kerf etc. Maybe check the focus and clean the lense?

did you check the lens? You need to regularly clean it. Otherwise, it will get dirty over time, which will lead to a disturbed beam first, followed by total breakdown.

I was going to clean the lens and when I did, I realized that the lens was clean but not screwed in all the way. Problem solved.