Initially, I crashed the first time I entered Lower City. Reloaded, had no problem. I was able to hop between Rivington and Lower City without much issue. When I went to finish the main questline with Gortash, I crashed trying to fast travel from Lower City to Rivington. No worries, I just reloaded and ended up walking through the gate at Basilisk Gate. That worked just fine.
I can't get back to Lower City to continue the story. I am soft-locked out of the rest of the game because I can't fast-travel back to Lower City or even walk through Basilisk Gate again. I was able to reload a previous save where I was already in Lower City just fine. I load to 33% every time and then it stutters and crashes.
As far as I know, I don't have the non-lethal damage bug. I don't really use non-lethal damage toggles except in specific scenarios and I haven't used it at all in either area in Act 3. I've tried every fix I've seen online. I was hoping to finish a full vanilla playthrough before restarting and using mods. That seems unlikely as this bug hasn't been fixed yet. It's been like this since September 29th. There have been two patches and neither have affected the bug. I'd just reload a save and go back to Lower City to at least be able to keep playing that character, but I've finished everything that I can do in Lower City so...I'm just waiting for this to be fixed.