By default, we use an item’s URL to determine whether or not that piece of content has already been published to a given social account. However, some content management systems change the URL when there is a change in the headline or a story is updated, which means that Autopilot could treat that story as a new piece of content.
RSS feeds contain a field called GUID (global unique identifier). Some CMS use this to identify a story with one consistent number, even when the URL changes.
If your CMS supports GUID, you have the option to use this to help Autopilot determine content uniqueness. The field can be found under Advanced Options while creating or editing a feed.