We are running Openfire 4.0.0 and have users running Spark versions 2.6.3 and above on Windows 7. One of our users prefers to go by his nickname rather than by his username. I don't know if this is the way he wants it throughout our chat architecture, but I do know that's the way he wants it for one group chat he's in. He has used this particular nickname in this group chat before, but every time he tries now, he receives the message, "Nickname in use, please specify another Nickname:".
As one of the admins, I've manually booted him from the room, combed the database for all instances of the nickname he wants to use, which only showed up in peoples' rosters, and manually removed those. I've cleared caches related to VCard and Roster. I've even gone so far as to have him completely log out and shut down his client, then remove the Spark directory from AppData.
Nothing I've done so far has had any effect in resolving this issue. It would be one thing if he just had to find another nickname to use, but this is what he does and eventually, the new nicknames wind up in the same situation. Is there something more I should be doing?