End travel does not work in 13w11a/1.5.1 pre servers

When attempting to travel to the end, most times you will cause the entire server to lag out,
the console will show "[WARNING] Can't keep up! Did the system time change, or is the server overloaded?"
everyone will get an "End of Stream" error, the server console will drop memory usage to around 200mb, but
it will show that none of the players have disconnected.

players can usally still use the chat without much lag for about 10 seconds, but commands don't work in either the console, or the client. eventually, after about 10-15 minutes the server seems to respond again.

tested with a locally hosted server, and a dedicated server.