Since adding a field into the field group would not prompt the user to name it, there is a possibility that the users keep adding the fields until they realize that the fields require a name when trying to save the field group. The user will be reminded of the fields that do not have a name yet from top to bottom. But, besides clicking the field one by one, the user needs to click "Save" every time to be redirected to the field that does not have a name yet.
Hence, it will be great rather than getting redirected, the fields are highlighted for those that do not have a name yet. (Maybe the box is in red)