Animation/Rig destroys mesh?

Hey there,
I hope Im right here. Dont be confused! Its a picture out of Unity, but I guess that the root problem lies in Blender. Recently I got a problem with a bow I just had imported. The bow has a simple rig and an shooting animation. As you can see in the pictures below the shader seems to be wrong (top), if the rig is applied. ![](/uploads/default/original/4X/d/b/0/db0ca516946e17bc1f67f28764ea1ac18328bb30.png)If I remove the rig its all working fine (bottom).
Where`s the problem? Thanks in advance!