Steps to reproduce:

1. Open attached project "733291.zip"
2. Open scene "tt"
3. Run scene
4. In game view, enable Gizmos and click on mesh found in scene and notice that rays go through mesh.
5. Console should print name of object each time it's hit, but it does not, therefore mesh is not hit

Workaround: Enable convex mesh collider

Reproduced with: 5.1.4f1, 5.2.4f1, 5.3.3p2, 5.4.0b8
Not reproducible: 4.6.8p1