A post was manually flagged as spam yesterday and when the post was unhidden the same user attempted to re-flag the post as the author hadn’t modified it sufficiently.
Instead of flagging the post correctly, Discourse returns the error “You are not permitted to view the requested resource”. Other users can flag the same post without problem.
Seems to be easily reproduced, have tested with a TL0 account posting and TL3/4 accounts flagging. Each time they flag a post the same account can’t then re-flag it.