This is a vanilla bug, not related to BSM. I don't think it's fixable either since it's part of the renderer code and that's still not released(and prolly never will be).
I made some progress with the 3d models this weekend, thanks to Deadhead. I can now export existing game models, import them to 3DSM and edit them, and then export them to the game format again. I guess I'll have my hands full the coming weeks
