I've had duplicate listings.
Sometimes when I'm creating listings, I notice that a listing is duplicated. I've wondered if it's something I'm doing, like hitting publish twice because it doesn't seem to publish the first time ... kind of a time delay type thing. But there are times when I think it's Etsy ... a time delay type thing on their end. When I notice, I deactivate the duplicate listing and use it for something else.
Once when I was using Vela to do bulk updates a whole bunch of listings were duplicated. Something to do with Vela I'm sure. Vela said no way, but Etsy support could see that the listings came from Vela.
And every now and then I've caught a duplicate listing. Could be me, listing something I've already listed. Could be I started a listing and saved as a draft and then created a new one later ... forgetting about the draft and then later published the draft.
I suspect it will be hard to pinpoint the cause, and even harder to get Etsy to fix. I recommend deactivating the duplicate and reusing it for something else.
