On the mission 'The Abbot's Gambit' you seemingly have to wake a drunkard up so that you can talk to him. So I pick him up and throw him in the river, just as you are told to do a mission earlier to wake up another drunk person. He proceeds to stand up and leave with no button prompt to talk to him at all. Normally when I experience a glitch to do with a npc I travel to Ravensthorpe and back and It resets everything but this however doesn't. I then load a previous auto-save and low and behold it doesn't work. It loads a different save, an auto-save made after the bug occurred. I load several more to no luck, they all now load the most recent auto-save made after this bug. I can no longer proceed with the main storyline.
I am playing on PC.