After an undetermined amount of time the data seems to desynch when a player has left/been disconnected from server but the server seems to register they are still there, then the server console gets continually flooded with below msg over an over untill your forcibly restart the server as it takes a long time trying to do normal restart.

Its also very common almost a gurantee to occur after the server has had a scheduled restart.

io.netty.channel.AbstractChannelHandlerContext invokeExceptionCaught

exception was thrown by a user handler's exceptionCaught() method while handling the following exception:

while writev(...): Connection reset by peer