I noticed that it will hang whenever there is a call on a check raise and that player is the last on that betting session, but he's the next one to call for the next session bet.
e.g. on a 2-player game
Player A checks after the flop.
Player B raise.
Player A call.
Turn card shown.
Player A turn to bet (it will hang here).
It happened on a game more that 2 players, as long as the last person to call a check-raise or re-raise is the first to bet on the next betting session.
You can verify if my observation is correct.