[Timiditas]

Was able to recreate the incident. I joined the empty server as spectator only and left again without joining a team.
Thing is, my server spawns one bot per default when you are alone. Since that bot leaves AFTER you leave, this plugin stops recording normally because on the second disconnect (the bot) it knows that no humans are left.
But if you never join a team, there is no bot that can leave after you, so the recording won't stop.
It is because when the forward OnClientDisconnect is fired, the disconnecting client is still registered as a connected client, filling a slot. So the plugin won't really register that there is nobody left.

I'll switch from OnClientDisconnect to OnClientDisconnect_Post. Will upload update in a few hours.