There isn't much I can do to prove or show this happening (as it always happens while I'm away or not looking), but Pucauto will commit to send multiple copies of cards I don't have.
For example last week it commit to send someone two copies of the new Olivia to someone even though my haves list only had one copy on it. The same thing happened with a copy of Shard Volley.
The output tells me it found x trades to someone with y points and then shows the card on the list twice.