Not sure why the system won’t let me post a comment with images attaches to it, but here’s the album on imgur - see Screenshots
So, it is hard to visualize this error with a simple box mesh since there are no forward-facing surfaces behind other forward-facing surfaces. I’ve replaced the mesh with a box mesh from starter content and applied a normal map for better visualization. As seen in screenshots 1 and 2, it still appears partially translucent and you can still see the world lines through the mesh, even when it should be fully opaque.
For better visualization I’ve also used the half-torus mesh from starter content and you can see in screenshots 3 and 4 it having same clipping trouble as the initial mesh.
In screenshots 5 & 6, you can see how the half-torus looks with the opacity at 0.0 and refraction index of glass at 1.52. It should be creating refracting distortions, but it appears completely see-through.