Sometimes 10% - 20% of the time when you make any world multiplayer, you get this weird bug when someone else tries to load. Ive tested this several times and I have also found a fix. When you start a world that is multiplayer, when someone tries to join the world they often times get stuck on "Locating Server" In the loading screen. And it can stay like that for hours. However... If you get a splash potion of Instant Damage and splash it at the player as his skin shows up in the world you can kill the player which can make the player join the world. 

Very weird bug hopefully you guys can recreate!

Thanks!!!