The server has been the target of a raid by multiple hackers tonight. They come on the server and immediately change their name to match someone already on the server. Then when the admin tries to ban them they get the wrong guy. That's what happened to fix, 13th Gerbil, Patriot and Goat Dog.
When you try to ban these guys if(when) they appear again, ban by Steam ID. They have no name against their steam ID in the menu, that's how you know you've got the right one.
Sorry to anyone who was banned by mistake. It took us a while to cotton on to what they were doing. It was only when they took my name that I was able to figure it out.