If any player leaves during the joining process while the dedicated host is waiting for all the players to join it will never start even if all the players needed have joined or all the players have left the server. That dedicated server will be forever waiting for players and wont revert to being a available host unless manually shutdown and put back up. The same issue is true hosting normally but in those cases its easy for the host to alt f4 and relaunch the game to create a new server.
Leaving while the server is waiting seems to create a phantom player. When the same player rejoins is shown 2 of that player in the game and it sits on waiting for players forever.
If this has a fix im not aware of i apologize. I already tried to search discord for other people talking about the issue but its a bit too specific to search easily.