Looking within the PZ3 I can see that there is an IK chain set on for the right arm. The  inkyParent of the right hand is eagle_winged_longsword:1. However the sword is parented to the hand. The goal of the IK chain is the right hand.

If you are having difficulty following that then it is very possible that Poser is also. :)

I hand edited the PZ3 to remove all references to the right arm IK chain. This was both the chain and the parenting lines within the actor sections. Save with new name.

Loaded this revised PZ3 and was now able to save an animated pose to the library and export out a BVH file.

Attempting to attach zip to this post.