People are using a bloody annoying invisible bug on my server. For more info: http://www.spigotmc.org/threads/invisible-bug.63281/

How it works?
1) Start and join the server.
2) Start a second client and log-in aswell on the server.
3) The first connected client will be logged out reason "You logged in from another location". (http://gyazo.com/d9540be7a8eb7f3a5665fb44a0989826)
4) Then your second one which you just logged in is invisible. Only when other people relog they can see the invisible guy again.

Example:
[10:24:39] [Server thread/INFO]: Fredse lost connection: You logged in from another location
[10:24:39] [Server thread/WARN]: Filtered out large getEntities call -37,-22 -35,-22
[10:24:39] [Server thread/INFO]: Fredse[/80.***.***.**:43993] logged in with entity id 1755 at ([world]-464.5, 16.0, -443.5)
[10:24:39] [Server thread/WARN]: handleDisconnection() called twice

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17.05 15:35:08 [Server] WARN handleDisconnection() called twice
17.05 15:35:08 [Disconnect] User Philip_Leet has disconnected, reason: §cYou have been kicked for idling more than 30 minutes.

I get that handleDisconnection for almost everything, not only when they logged out in another location.