Michael please try this and see if you see something wrong with the "subDiv" elaboration.

I've made with V3. It's a very simple use-case.

The red mark id where I think there's some strange "flow" but i don't know. Please check the entire model if you can.

Hope this can help :) This is the best I can do right now.

This is the 3dm file : http://take.ms/rhLTD



Ciao!