My world is quite old, and we've been using it for at least the last two years, if not more. However this latest update has given us more issues than normal. First in July I decided to go exploring, only to start receiving a crash and then more crashes, and I ended up having to download the world and delete the latest chunks and then tp myself out of there upon reuploading it to realms. That seemed to solve the issue. 

Now, I seem to be getting the issue again. I was exploring and loading new chunks near my base and was kicked off with a message saying 'server closed', I then tried to log back on and got the following:

io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: no further information:

I then tried turning the server off and on again, only to have the same issue upon logging in. I loaded up a new world and had no issues exploring. I restored the world from a backup and had no issues either. Other people went on the world after we encountered this issue and did not get the 'server closed' message, yet when I went on everyone was kicked and got the message, then the second one upon trying to reconnect. This is the exact same as what happened in July, though I can not remember if the message was different.

 Edit: A friend joined the server after I had reset it and went exploring and it crashed for him as well.