A few things you reported are now fixed:
Fixed
Discarding duplicate tiles: With two identical tiles, the game sometimes removed the one from your run instead of the one you clicked. Now exactly the tile you choose is discarded.
Rejoining a lobby: The game could get stuck on "Connecting…" and needed a restart. There's now a Cancel button, clear error messages (room full / gone / game already running) and a timeout.
Ghost rooms: Left rooms stayed in the room list. Rooms are now left properly, and running games are no longer listed.
If the host closes the room, everyone returns to the main menu.
If you spot anything else, let us know in the discussions.