Don't need a fix for my site in advance of any general fix for what I think is a little bug here:

If you're dealing with a Group Custom Field in the back-end and you delete 'News' or 'Discussions' - then you reinstate them (because they are mandatory fields!).. they return with 'Set a title' and 'Set a description' for their title and description - presumably this should be some better default wording to explain what they are, similar to what you get for photo and video custom fields if you do the same with them (delete then reinstate).