I have Evernote 10.5.7 for Mac and the most current version for IOS. I just started having this problem. I create or edit a note and the next time I open Evernote there are 2 or 3 additional, identical, copies of that note. It really makes the product difficult to use.
I have also noticed that the newest version of Evernote automatically tags a newly created note with the tag of the last note that was open - also infuriating.
I've used and loved Evernote since 2006 (!!) but you are going to lose me if this is not fixed very soon.