using linuxcnc for laser fiber marking

A possibility is that the acceleration (or velocity) is now _too_ high and the actuators are skipping steps. Note that I don't know if this is even possible, I don't know what the internal actuators are in your galvanometer (I have one driven by stepper motors, but that is more intended for position indication in a manual PCB assembly system)
This frame from your video would appear to be consistent with this possibility.

Does the galvanometer have any specifications for angular velocity an acceleration?

in fact galvo, haven't stepper motor , it uses a special actuator, This is a picture of it:
 

I must also say the problem is not the hardware
I checked the position command from start to finish
The last place where the position is stored is the pid controller,  The speed is then used to command the xy2-100 hal component , and position of xy2-100 output (in software) always is same with hardware output.
i think the problem is pid !

If you don't get following errors, the PID is not the issue
What are your following error limits?

PCW wrote:

If you don't get following errors, the PID is not the issue
What are your following error limits?
 

I do not have following errors

What are your following error limits?

PCW wrote:

What are your following error limits?

Sorry didn't notice

FERROR =    .020
MIN_FERROR = .002