Realms Join Bug

If you open a second Minecraft after loging in whis a first one in to Realms,
and than join Realms whis the second Minecraft, you get disconnected whis the first one and the second one login.

But in the chat is only a message, that you left the Server and your name is not in the player.

Step by step:
1. Join Realms whis Minecraft.
2. Open new Minecraft.(do not close old one)
3. Join whis new Minecraft the same Realms Server.
4. There is only a message that you left the Server and you are not in the player list.