Same here man and it's super frustrating. I've put in a ticket with Larian with no answer yet. I'm on PC and this has happened to my second character in act 3, what's weird is it seems to be region specific. I found out I can travel back to the Rivington area and save. I even venture forth complete some quests and travel back to Rivington and save. Those that have beat the game can understand this isn't a viable way to play. I'm pretty reluctant to put in many hours on a third play through bc that would really suck for it to happen again.
