almost 2 years ago - AndrewT - Direct link
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, refresh rate 60.

Is that any better? If not,
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  
almost 2 years ago - AndrewT - Direct link
Looks like your AMD video driver could stand an update, so install the latest from here:
http://support.amd.com/en-us/download
Then let's do a clean reinstall and eliminate those mods that are giving errors:

- 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.
- then redo the steps in my previous post
- start the game with no mods active and test with a new campaign, NOT any existing one.

Good luck!