Not quite sure how you will diagnose or review this given details, but worth sharing.
There was just a case where a photo was being blocked as a copyright violation despite the flag on it being resolved.
The 2 flags are here, they were added in 2018 by accident, while the photos came from a stock agency with watermarks the iNat user was the photographer so owned the copyrights. Both flags were resolved in 2018.
I suspect the search link above will fail due to what is listed below, but perhaps on the backups or logs etc it will help.
Recently somehow the original flagger saw the records and it was back to media removed despite the flag resolution and no new flags and commented on the record asking why it was blocked again.
I started to look into it. But her comment led to a notification being sent to the user who got angry at being accused of copyright violations and or this specific issue and has apparently deleted their account out of anger which will make looking into it harder.
Perhaps looking into what is showing on other records that have resolved copyright flags?