Connection lost could not connect to a default or fallback server please try again latter:io.netty.channel.abstractchannel$AnnotatedConnectionExpactaion
Your sub server or your bungee server may be misconfigured. Check the sub-servers IP and see if you can join the server.
If that does not work try to restart the server. If you're unable to join that sub server there may be a bigger issue.
Try to double-check the ip and make sure the server is online.