This hapenned right after the update, some users can't use the @mention function at all - when trying to do so, they get an error message, I will attach a screenshot.
I briefly read through some older posts, that point out that it's a "content index" related issue, which requires Atlassian's output.
I've verified that the Global and Space permissions give access to the people that can't use the function and also the people that are being mentioned.
