Hi there,
I think this is more a divi “issue”, but it could be fixed without code.
I suggest to modify your display rule for your copyright field and store it directly in your post.
It’s not as user friendly as storing it in media datas (which could be used within divi editor).
But it should be correctly display from divi.
Possible explanation
Divi probably looks for your image copyright value in your post metas.
The value of your acf field is not directly stored in your post metas, but in image metas.
Your post metas just store the featured image ID.
So when Divi search for your copyright field it doesn’t found anything as it’s not related to post ID (which divi probably gets from context there).
Hope it helps a bit,
Rémi.
