[2020] Game suddenly slow. Help!

This has worked for others, so Please do a full **clean** re-install:

- move any valued save games elsewhere
- "uninstall" in Steam-CK3
- manually delete both the Steam/SteamApps/common/CK3 AND Documents/Paradox/CK3 folders
- 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.
- start the game with no mods active and test

In particular make sure there are no files or folders left under either the Steam CK3 or Documents CK3 locations, before installing again.  

No, I don't, as yet anyway.

We could try just some limited steps to try and narrow it down. What if you go to documents/paradox/ck3/ and just delete the three cache folders?  

papaGiorgio said: Well tried deleting all four just to try. It did not help.

That's a shame ... how about if you delete the whole documents/paradox/ck3/ folder (except any valued saved games)?

papaGiorgio said: Of note, there are two instances of Crusader Kings III in my allowed apps for windows firewall. They are both checked to allow, but I'm not sure why I have two instances.

Probably different versions of ck3.exe , perhaps 1.1.1 and 1.1.2 . In any case this is not a firewall issue.