The head in the video (and other body parts) drops in and out of visibility, perhaps it is being occlusion culled rather than an issue with the camera's mask. iirc There are settings on the renderer that control this.
This issue is related to bounding boxes. If you compare the demo scene Nolan you will see how the bounding box roots are setup. Most have the root as hips bone, the helmet has the root as the head bone.