Has anyone else found that the @mention dropdown menu doesn't always show up and when you hit post, the link isn't recognised? Any way to fix this so that any word with @ infront of it automatically becomes a mention?
Have you checked the 19.12 release notes which talks about a fix related to @mentions? - "We have fixed an issue where the @mention drop-down list was not showing the correct results even when the exact username was entered in the UI. @mentions is now working as expected."