There are several reasons why you can encounter that kind of situation, so we'll look into each of them separately:
Your creative will always be duplicated if:
- You're promoting a post, but you're using placements that differ from the original one (for instance you're using a Facebook post, and promoting it to Instagram, it usually duplicates when adding to the IG Feed).
- If you're adding the Instagram of Facebook Stories placement, it will always duplicate your creative.
- If you're using a tracking strategy that rewrites the URLs
- When you are editing a creative, you are not actually changing the existing post, but you will duplicate the post, and edit the new one. That means you will end up with 2 posts, and your engagement will be split.