This has been happening to me since about April.
Everytime I edit/add a note on Evernote Web, it starts to create copies. The longer that I leave the EvernoteWeb tab and that note open, the more copies it makes of the note. Even if I've not changed note, it makes a duplicate. I've had 27 duplicates of the same note that I had to go through to check it was the latest version, just because I left the machine and went for lunch.
This doesn't happen on the windows desktop clients. But it happens on a windows platform in Evernote Web.
On my Ubuntu machine, I've tried both Firefox, all updated, and Chromiu browser, all updated. But Evernote Web keeps duplicating notes.
The duplicated notes then sync to my android Evernote App. It's incredibly annoying, and is hamperimg my ability to work across my platforms - which was the whole point of Evernote in the first place.
Any fixes yet?