Engraving difference

This can be caused by following a vector. The second pass or the return pass has a head-start and can over-cook a good line.

If you’re willing to share your LightBurn project file here we may be able to recommend another setting or another approach.

I would recommend treating the wood with a water and Baking Soda solution to make the material more sensitive. Brush on the liquid, let it dry then repeat the Material test.

With the treated wood you should be able to get more evenly shaded results at lower power.