The game crashes under various conditions

Right click on ck3.exe , properties, compatibility. Tick "disable fullScreen optimisations" untick every other box in that dialog, Apply and exit.
Then in the launcher Game Settings menu, select fullScreen display mode, Vsync off, cap refresh rate at 60.


If those don't help:
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.

Please attach here your Documents/Paradox Interactive/CK3/pdx_settings.txt .
From your Documents/Paradox Interactive/CK3/logs/ folder, attach here system.log , error.log , exceptions.log  

Looks like you haven't done all I suggested:

"vsync"={
version=0
enabled=yes
}

Please do these steps:
in the launcher Game Settings menu, select fullScreen display mode, Vsync off, cap refresh rate at 60.

And please instal the 2024 nVidia driver

Download the latest official NVIDIA drivers

Download the latest official NVIDIA drivers www.nvidia.com
IF they don't help:
That error log is full of saved game problems. Are there any mods in use here?

If so please move all saves out of that folder for the time being, then start a new unmodded campaign. If you still get these problems then, attach here new copies of all those files. Thanks!  

For a full **clean** re-install:

- move any valued save games elsewhere
- "uninstall" in Steam-CK3
- unsubscribe from ALL mods in the Steam Workshop for this game
- manually delete both the Steam/SteamApps/common/CK3 AND Documents/Paradox Interactive/CK3 folders - In particular make sure there are no files or folders left under either the Steam CK3 or Documents CK3 locations, before installing again.
- re-install game in Steam, run a Steam Verify when done.
- add CK3.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.

Unload GeForce Experience.

Right click on ck3.exe , properties, compatibility. Tick "disable fullScreen optimisations" untick every other box in that dialog, Apply and exit.
Then in the launcher Game Settings menu, select fullScreen display mode, Vsync off, cap refresh rate at 60.