I've been getting the same problem (crashes loading lower city at 33%). I had just killed Gortash and was on my way to fight Orin.
I DID SOME TESTING AND I FOUND OUT WHAT CAUSED THE CRASHES FOR ME.
It was the Steel Watch trying to arrest me.
If the Steel Watch is trying to arrest me on sight, the game would crash at 33% when trying to load the lower city. If the Steel Watch is chill, no crash.
Plz test for yourselves, load the latest save you have where the steel watch is not trying to get you and travel to rivington and back to lower city to test. I lost like 10 hours but I'll deal to save the 100 I put in already.
I'm not sure yet how to kill Gortash without making the Steel Watch angry but I think with this info I can trial and error my way to the end.