You are right. I need make changes here. I noticed that when working on the rotation for thumbnails. I initally did this, so that the "metadata" object does not get replaced by createThumbnailAndPreview callback, which itself returns new metadata object ("m"), in order to carry the orientation through. So far this was never an issues since fullsize image and thumbnail both had a shared set of properties ("width/height"). I need to look into this again.