However there are generally a couple common reasons this could be happening.
- You accidentally have the snippet on the page 2x. I've seen where it's added via a tag manager and in the HTML before. You should confirm the snippet is only loaded once.
- Open the edit code in the variation and make sure you don't see the banner image URL in there 2x. You could be duplicating code.
- Finally, make sure you are not accidentally also adding the banner through another, separate experiment that could be overlapping on this page.
Looking forward to hearing back from you on the additional details!