This is happening to a lot of people and when you try to connect a server running bungeecord with forge installed it comes up with an error saying "ReadTimeoutException : Null" after spending about 1-3 minutes logging in it shows that error message.
I have tested this on The Hive and they cannot fix it so I am hoping Forge are able to fix this.
Not entirely sure it's bungeecord but that is what I was told.