This problem arise because when a robe is worn the characters arm meshes are removed instead of "covered". This is necessary because otherwise it would be too difficult to sync the robe mesh movement with the arm mesh to cover it all the time, so it's better to remove the mesh instead of covering it.
Problem is along the arm mesh also the bracers attach point are removed, missing an attach point the bracers mesh are displayed at the character's feet (should be the 0,0,0 relatice coords if I'm not wrong).
Looks like a fix is not easy or straightforward.