When in the By Component Tab of the sh404SEF® Settings a component is set to "Use Joomla router" in the first column it will use the Joomla router. When the Joomla router is used instead of the sh404SEF® router, URLs for this component are not recorded in the database and duplicates are no longer be prevented for this extension. Since this option no longer makes sh404SEF® the sole URL rewriting component it can no longer apply the custom 404 page and new 404 errors will no longer be recorded and displayed in the 404 manager.