Hey all, just registered my account to leave my 2 cents. I'm experiencing this issue too. I can confirm the issue starts in my case after killing Gortash: if I try to fast travel to the lower city before killing Gortash, no problem. If I do so RIGHT afterwards, crashes at 33%. No troubleshooting worked so far.

I only have the Tribunal of Bhaal left before the endgame so I hope this is fixed soon!