Hello, did you fix your problem or still not? I'm asking because I am facing probably the same problems :-(
Playing late game, I rule half of the known world, but approximately a week ago my game started to lag/freeze = first it runs normally, but after some time, it completely freezes and after e.g. 1 minute, it continuos playing as nothing happened. Then it happens again in few minutes. Plus the game starts to be a bit slower/laggy in general. Then I get into the point where the game freezes again and it takes e.g. 4 minutes before it goes again. Btw. meanwhile it is frozen/autopaused, I can scroll on map, check characters, anything, but the actions and decisions I make, or pop up ingame messages will appear always after the freeze ends. Then games become quite unplayable = 5 minutes playing, 4 minutes of freeze, over and over.
Before a week ago, I didn't have these problems at all. Even in past, I already ruled whole CK3 world and there were no lags, no freeze, everything running great on highest details. I also played Iberian Struggle in other previous game recently and I didn't have these problems (but I didn't control half of known world yet).
I tried install new graphic card drivers, reinstall CK3 + follow all the steps written above in this topic by AndrewT. Then I also changed game graphic to medium. In WIN10 I see that my memory is on 80% when I play CK3 (all other programs closed).
This is my PC setup, but as I told you: a week ago, maximally 2 weeks ago, these lags didn't exist :-(
Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz 3.30 GHz
RAM 8,00 GB
Radeon RX 570 Series
WIN10
Thank you for any tips.