So uh
I'm at the ending of that dlc where i want to help Olgierd but every time when i'm about to finish magical world where o'Dim teleports you game keeps crashing every single time and idk what to do anymore
Exact moment where it happens is at this fountain where u need to use Aard

I had the same issue and managed to get around it. I'm not sure what exactly did it, but I set the Display option to Windowed Fullscreen, turned off Ray Tracing, turned off all effects, and set all graphics settings to low. After that the cutscene played as intended.