Similar issue here on M3 Pro. Noticed a slight performance drop after the latest major patch, but continued playing. But a few days ago there was another small patch and after that sometimes during the dialogues FPS drops massively (to about 15 or so), depending on the camera angle. Very annoying. Tried cleaning cache, fresh install, nothing helped. Even the Lowest graphical settings didn't help a bit (before I was playing on high-medium with no issues).
What aspect ratio are you using? oddly, part of the fix involved a change to the aspect ratio.