You can only have 1 article with the same name in a namespace. Why? Duplicate names would have the same URL. This is why the rest SEEM deleted; there's no way to access them. If you need more than 1 article with that name, then you need to move it to another namespace so that its URL will be different, or you need to use inline moderation to rename the "hidden" threads.
You can see the text of all the conflicting names by going to VaultWiki > Wiki URL Manager, and finding the troublesome URL in the list.