i prefer to edit those things manualy in 010
I checked it out in 010, and I saw that in the right shoulder bone in the bone struct it had ABlock_S Rotation. Since the only thing that seems to be bugged with this model is rotation. It only contained hex values, and yeah that is the point of this editor but I have little to none experience with those kind of values.
Not sure if I'm editing the correct things, but if someone could point out where and how you edit the rotation to turn the shoulder around that'd be great.