If the tutorial NLG system has scheduled messages for sending when the user leaves the tutorial room, these messages will still be sent, interspersed between the messages from the new NLG system. This happens e.g. if the user ignores all messages and leaves the tutorial room straight away. This probably happens because the DelayedSendingThread is only interrupted, not shut down. Problem might be fixable by simply replacing "interruptSendingThread()" in TutorialNlgSystem#connectionDisconnected by "currentSendingThread.shutdown()", but I've lost track of the creation and deletion of sending threads in TutorialNlgSystem, so this should be done more carefully.