I am pretty new to wintermute, but I think the problem is because of your model. I had pretty similiar problems when I used a model with bipeds. This model did not had assigned all verticles to the right bones, and I didn't was able to fix it up... however I switched to a model that is made entirely from bones. That worked out for me fine...
I know this is not a great solution, but wanted to say what I experienced with those problems and how I gone through it
I guess the real developers can help you more soon about it
