I recently upgraded to Luban 4.8.0, and one of my models is oddly generating a layer of printing where there shouldn’t be one. I’ve included a screenshot of the model, a screenshot after I generate the g-code in preview mode, and a link to the model
Increasing from 0.8 thickness and 2 wall lines to 1.6 and 4 wall lines helped. I didn’t want to do this, as it increases print time and is unnecessary, but I’ll take it until the bug gets fixed.
Usually that means there’s a problem with the mesh in your model, and the slicer thinks there is a layer there. Open it in a tool that lets you see the mesh directly, like Blender and see if it looks right. There are many posts on the forums about diagnosing and repairing meshes. When I import your linked model, my Luban says it has errors. That’s not a guarentee of a problem, but it is suspicious.
FWIW, I’m not seeing that when slice on 4.8.0, repaired or not. Even with a layer height of 0.04mm. But that part is too big for my bed, so I had to shrink it in the X & Y direction. The latest Cura won’t let me slice it at all.