I think I've compiled some new-ish informaton about some bugs.
After every round, when everyone is sent back to the start screen, the selected map doesn't change for a few seconds, so if they tr to re-join too fast, they get sent back to that map an get stuck. They can't get teleported to the Waiting Room or the map the the next round will be played on when the round starts. At the end of the round they remain stuck there and don't get sent back to the start screen.
No one seems to get deleted when they log out. When they log back in, their mob gets teleported to the start screen. King Goomba thinks it has something to do with the absence of a del proc.