Sandis: I know it's kind a late, but better late then never, one way to fix this is to do with stash chest, I had this infinite loading screen right at the same place, exactly after Geralt and rest of the heist crew stop bickering and pick up the wooden swords, I was testing everything out and just couldn't find the way to fix it, but after exhausting tests, I found the solution, and it worked for me, it turned out that I had stashed some vital items in that chest (I had mod Unrestricted Move-Sell quest items!), I moved everything what was inside back to my inventory and 'Vola, infinite loading screen was gone and it worked as intended, hopefully this information helps!.

Note: Alright I pinpointed the exact item, it's the wooden sword, I stashed this quest item from quest (crimson avenger), and it was the item that caused the infinite loading screen in (Heist) quest!.