Constant crashes and frame stuttering since first patch

Prior to the first patch, I ran this game on high settings with an average of 90-100fps, with occasional dips down to 75, but nothing below 60. I played the entire game (up to the final quest) completely fine with no bugs and 1 crash in around 55 hours of playtime.

Since the first patch, my game refuses to go above 60, with frame stuttering and drops constantly- especially during combat and cutscenes. I have tried everything: setting all my settings down to low, playing on ultra performance, verifying game files, uninstalling and reinstalling, moving across from 1 ssd to another, limiting my fps. Nothing fixes the stuttering or crashes. 

I'm playing on PC through Steam. My specs are intel i7, nvidia 4060, 8gb VRAM, 16gb RAM, Windows 10. No idea why my game has suddenly become unplayable since the patch and would appreciate help or other solutions. 

The first video is what my game looks like now (until it crashes after 30 minutes playing) and the second is how my game used to run prior to the patch.