You have an error that's directly fixed by the link I posted.
Do see if it helps, because many thousands of hours of testing was done on dedicated servers including linux and this hasn't been seen, so more troubleshooting and debugging (if needed) is needed. As it stands, this doesn't reproduce:
1) Run dedicated server
2) Have people join, disconnect
3) Players will still appear in the server list as connected, a yellow error will be spammed through the console.