The server is setup so that players get kicked for 5 minutes after doing 300 team damage.
When this happens - they get added to the banlist for 5 minutes.
However, upon using !unban <ban number> the ban is removed from the banlist, but the player is still unable to connect to the server for 5 minutes.
Even after opening a new client, they still recieve the message you are kicked or temp banned on the server. (or something similar)