Weird transparancy in the the render mode for a mesh

Hello, I have a display issue with my model in the render mode. The mesh looks transparent but it only happens when I turn on the shadow. I have tried to convert the mesh to polysurfaces but this still happens. Can someone give me a hand on this? Thank you

Mesh Weird Transparency.3dm (293.5 KB)
Copy of Rendered.ini (12.8 KB)