As anyone who runs a coop server can tell you, Coop servers tend to be unstable and tend to crash.
Sometimes if a player is in alone and leaves at the end of the map BUT before the map changes it may cause others not to come on. They die and then get disconnected. There is nothing I can do about it but restart the server.
Other problem is when players don't move off spawn points fast enough, Because i am running a OneTeam mod players can't kill eachother so they may end up stacking on top of eachother due to few spawn points and can't move or kill eachother. Only 2 things can be done, a player can kill himself or rcon can kick the one who is not moving.