Hello,
I bought a K40 a while ago, and until now I didn’t face any huge problems. However now when I engrave it seems like the laser is skipping some parts. Like this
Before this what it looked like, and now it looks like this. The laser cuts normally but the engraving is the problem.
Anyone got any idea what might be the problem?
I want to check if my optical elements are clean and if the alignment of the laser beam is still in the center on all 3 mirrors and if the nozzle is at its 90 degree angle in both directions. Finally, focus must be checked. It is also possible that if you have not used the machine for a longer period of time, that the tube itself no longer has the same effect, unfortunately, just like us, it gets older and older 
But then you have to adjust your values a bit, until it fits again.
Just to make it clear, this is a file you have run in the past without any problems?
From prior posts it looks you are running K40 Wisperer?
What power (mA) are you using for engraving?