Unfortunately, I'm not able to reproduce the issue with Sitefinity 6.1.4700 with the following RSS link http://feeds.reuters.com/news/artsculture. When I run the feed in News section I have the news items only ones (without duplication).
Could you please verify if there are differences between your staging and production environment?
Could you verify that you've followed the standard procedure for feed creation?
Does this behavior reproducible with all RSS feeds or with one specific feed? Could you please try to create new feed from different external RSS and check if the news items are duplicated?
Could you please try to recreate this feed and check if the news items are duplicated?
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