I know this has come up here before. Taxonomies do not work the same way on media as they work on other posts. I know there are some things that need to be customized, but my memory is foggy, it was a long time ago, and I can’t find anything.
I think that you need to create your own acf/load_value and acf/update_value filters in order to apply the terms to the posts, but that’s just a guess.
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