I have also experienced stutter when casting some spells but also at sudden intervals, freezing: game screen freezes completely for about 6 seconds before running smoothly again. I did not have this with previous patch, but it can't be that widespread, othewise more people woudl have complained? I also have RTX 3070, 16 GB, but intel i7. I have tried using fullscreen vs fake fullscreen, bvut haven't turned trn graphics settings yet.
