Sorry to hear about your problem with the game. That's odd since this is a first bug report on something like this. We will definitely look into this but meanwhile please try to quit the game, then start a new game, exit back to main menu and then restart chapter 6.
Thank you for the suggestions but sadly the issue still happened. I also tried downloading the Windows version of the game to my wife's system that runs Windows 7 Pro SP1 and bringing my saved game over and it happened there as well so I think it is either a corrupt save file or an issue needing patching. It has happened on Solus Linux as well as Windows 7 Pro 64 so it's not OS specific. I will start from scratch and see if it happens again.