This is called lag compensation. Lag is a term indicating the tendency for delay of a particular Internet connection. More lag means a longer time is required for a player's moves to be communicated to the game server, which can make it seem as ...
The system automatically considers that the player has left the game due to a bad internet connection or if the player was switching between the windows. If you are sure that none of these cases has something to do with your game, this might be ...