Still, you can fix those just as easily with post just as easily as I fixed the tops of the collars, but I think your collars are not far enough forward to allow that much tweaking of the shoulders. Poser was not truly invented for rendering finished works. It was designed to demonstrate form so that artists can shape it into finished works in the post stage. Anyway here's an example of a similar pose with the collars pushed forward more and the shoulders set closer to zero than in your pose. There's still a tiny bit of jaggedness along the front of the shoulder, but much less than with your pose. Still, I have not found any way of avoiding post work. The top figure is Vicky and the bottom figure is Saluda.