Wow! Fantastic to see one got nailed down already!
I haven't played in a while, but as soon as I installed Chapter Two and had the new quest going - long saves exactly as you described, around 70 seconds the first time. Actually thought the game had frozen before I remembered your post so waited it out, and sure enough, it finished and the game continued about its merry business as if nothing had happened. FWIW to any bughunters better at this than I, I noticed it didn't seem to matter if it was an autosave, a manual save, or either of these triggered by something else (the game's own autosave, hotkeys for either, etc.).