Change "transform.LookAt(PlayerController.instance.transform.position, -Vector3.right);" to "transform.LookAt(PlayerController.instance.viewCam.transform.position, -Vector3.right);" so that the object looks at the camera instead of the player. Also, you should use LateUpdate for the billboard code, not Update, since if you use Update it will be consistently one frame behind. Also make sure you remember to drag and drop the billboard script onto the gameobject that you want to billboard the player before you enter playmode.