Anytime The End or The Nether is entered or exited, it kicks everyone in the game and gives a java error:
Internal Exception: Java.ioexception:received string length is less then zero!
Weird string!

I recreated this issue and found that 4 players can stay on but when the 5th person logs on everyone gets kicked. Also, when a person enters or exits the Nether or the End all players get kick except the players that are in the Nether or The End and gives the same java error to those same players.

Note:all players are getting kicked except for players in The End or The Nether