After connecting to a server, I was after a minute or two disconnected with an io.netty.handler.timeout.ReadTimeoutException.

When I go back to the server list, the server says that 1 player is online. Hovering over the player count, that player is myself.

Attempting to reconnect immediately displays the same ReadTimeoutException. For whatever reason, the server thinks I'm still online and that causes any additional connection attempts to fail.

I tried to kick myself using the server console, which displayed “Kicked Fenhl from the game” but didn't actually cause any changes to the server status.

The bug affects the same Survival server I mentioned in the comments of MC-61128 (after the server restart that fixed MC-61128 for me), but not the Creative server, so the two issues might be related. Restarting the server again fixes this but causes MC-61128 to occur again.