Hi Wedgie - so yeah the vertex normals that come from the vertex normal map are used to shade a mesh with light sources. So if your mesh geometry is transformed but the vertex normals just stay in their same orientation it will make a weird effect where the object gets shaded as if it hadn't moved.

If I remember right, Modo will transform the vertex normal map along with the object only if you are in "Item" mode when doing the transformation.

So that's probably the key thing to look for - what mode are you in when doing the transform for the mesh spin? If you're in vertex mode or face mode or whatever, try instead being in item mode and see if that works for you.

It would be nice if Modo would transform the normals in other modes as well if the entire object was actually being transformed anyway (like if all vertices were being transformed in vertex mode, etc...) maybe that's something they can improve in Modo in the future.

- Michael