Try turning off V-sync in Miscellaneous. Just got this issue after the update few days ago and this did it for me.
Turning monitor off and on again also bring fps back to normal but only temporary.
I just got a similar issue today, managed to find 2 fixes if this helps. 1 temporary fix is just turning my monitor off and on again, that got everything running smoothly again. The other fix which did it for me was to disable Vsync. Before this the fps drop happens about 5-10m into the game, just ...