When using the SSS shader, if you transform/warp it from it's original position, and use it as a mask, it seems to leave "shadows" of it's original location, without it showing on any 2D previews. The "Shadows" seem partially visible, so it leaves a "faint" mask of it's original position.
I posted about it before, getting not much input except to use image maps. This happened on my tire tracks setup I was posting for help for someone.