Shota tag added is the reason. That sort of tag is used specifically for anything heavy on the sexual level.
Sometimes I wonder if there should be some kind of pop-up any time a Member-level user tries to upload a post with a restricted tag, warning them that they'll be unable to view it or further edit the tags.
Then again, that would probably encourage some of them to simply stop using those tags even when they should, so maybe keeping the status quo is for the best.