Cura Closing holes

[JDoub 0]

When I slice my model holes (Hugh Holes are closed. Why? I want it to print like the Prepare version not the Preview version. As you can see in the 1st photo they're a several holes where you can see the "Shadow" on the build plate, most notably the two holes in the center of the model. But when I slice it the holes are close and infilled. This makes no sense to me. Why?

Cura 5.3.0_mac

Front Rail Section.stl

[ahoeben 1,992]

Probably because your model is "non-manifold". All walls need to have a thickness.

Read this article: https://github.com/Ghostkeeper/SettingsGuide/blob/master/resources/articles/troubleshooting/missing_parts.md#non-manifold-meshes

[JDoub 0]

Probably? Did you even look at the model? All of the walls do have thickness, there are no non-monifold parts.hh

[obewan 37]

Try with union overlapping volumes unchecked