There are two main reasons why you might see duplicate carousel cards in an insights report:

• If you used the same headline for different carousel cards, you might see what appear to be duplicates in your insights report, but are in fact different cards.
• If you edit your ad multiple times, you may see duplicate cards in your insights report. That's because each time you edit your ad, we generate a new ID. To avoid seeing duplicate cards in your report, it's recommended that you create a new ad rather than edit an existing one.

* Nguồn: Facebook