(Sorry, don't have lobby number. Happened about 18 hours ago on pl_upward NA HL.)
We readied up a lobby but it closed due to excessive subs almost immediately after it started.
Here's a guess for what happened
1. lobby readies up
2. one player (not the leader) joins server before all others
3. that player has to leave, reports herself, and disconnects
4. TF2C thinks that too many of the players (0 in game?) have been reported and ends the lobby.
Thanks