Hi, I'm using the ProBuilder API to build custom meshes. Below is the example I'm working on: As you can see, the selected face is an "inner" face of the surrounding face, which is: Problem is I can't extrude the inner face: when I extrude, it just moves and pulls the surrounding face, as if I was just moving the Z direction gizmo: When I debug through C# and look through all the ProBuilderMesh properties, everything looks fine: vertices, faces, etc. I tried doing it on a mesh I built through ProBuilder interface, and it works. So there is obviously something dirty in the way I build the mesh with the API, and I can't find what it is. I'm really stuck and help would be greatly greatly appreciated! I uploaded a package of the mesh if anyone wants to take a look.