This can happen occasionally when you upload a new image with the same name as a previously uploaded image.
Even though the image itself is different, the file path is the same, and so the servers look for the original file stored under that name (In this case, the older image.) The easiest way around this is to rename your image to a unique name.
It is possible for support to flush the cache to remove the old images if you would prefer or must use the existing name, but it does take some time.
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