Looks like a “fourth corner” problem, as discussed elsewhere:
https://forum.lightburnsoftware.com/search?q=%22fourth%20corner%22
The general procedure is to get the beam aligned & centered on both Mirror 1 and Mirror 2. Then you align & center at the entry to Mirror 3 with the gantry at the rear of the platform, which will inevitably mean it’s not quite right with the gantry at the front of the platform.
If so, then:
- Mark the entry to Mirror 3 with the laser head in the left front corner
- Move the head to the right front
- Adjust the Mirror 1 vertical screw in very very very tiny increments to move the right-front spot so it overlays the left-front spot
The Mirror 1 vertical tweak will be tiny, so be careful!
My experience may be helpful:
Tiny tweaks! 