I see this happen all the time.
After a match ends, you can click "Ready" to try to join the next match.
But often, the Ready button deselects itself.
If the table host changes some table parameters, this will invalidate the "Ready" by other players (like you want to play a 2P game, but they open antother slot for 3 or more players).
If that happens when you are the host, that would indeed be a bug.
Does the opponent proceeding past the "Game is over" prompt, and on to the After-Game screen trigger unreadying?
In my tests it looks like if the table host goes from "The game has ended" to the end-of-game screen, any "Readies" from other players are removed.
Since automatched games only have a "host" because the one player has been designated as such, do you think we can ignore the rule that automatically unreadies players if the host returns to the room? Just for the automatched games.