Some users get duplicates when annotating PDF articles using PaperShip and then sync them with Mendeley or Zotero.
It is usually related to the fact they “watch” folders on desktop, which can conflict with how the platforms are available to 3rd party apps like PaperShip.
It can also appear if you sync your library with other cloud services like Dropbox.
If you use PaperShip and watch folders on desktop or sync with Dropbox, we strongly recommend you to turn off these options and you will no longer get duplicates.
Contact us at email@example.com if the problem persists.