Please raise a ticket with Support.
I did hear something this morning where smart lists were snafud.
I haven't seen that, I've seen missing marketoGUID in bulk export and I've raised a support ticket but don't have resolution yet. I've been away from the project a little while I'm waiting for resolution. I haven't seen duplicates but honestly I was stymied by the lack of a key and didn't notice one way or the other. I'll follow up if I see similar.