The line on the X-axis is shallower than the line on the Y-axis

The spot from a diode laser is not square and will typically produce a darker mark / burn when moving parallel to its long axis.
The specs for the 40 W laser head say this:
Laser Spot 0.1*0.15mm
That implies the long side of the spot is parallel to the Y axis, which agrees with your observation “lighter on the X-Axis than […] on the Y-Axis”.
It’s inherent in the nature of the laser, so there’s no way to “fix” it. Basically, you must arrange your designs to either take advantage of the shape or minimize its effects.