I emailed Larian Support and was told this bug should be fixed in the next big update (no ETA). They tested one of my save files that has the exact same issue described in the OP (I can load into the game once but any reload or load back to the menu causes a crash, which has led to me being unable to load Act 3 as it crashes almost as soon as the cutscene starts). I was told the bug was fixed on their current internal build so it's just a matter of waiting now.
