CK II - Black banners 3.1.1

[tostman]

One line summary of your issue
Black banners 3.1.1

Game Version
3.1.1

What expansions do you have installed?

Monks & Mystics,
The Reapers Due,
Conclave,
Horse Lords,
Way of Life,
Charlemagne,
Rajas of India,
Sons of Abraham,
The Old Gods,
The Republic,
Sword of Islam,
Holy Fury

Do you have mods enabled?
No

Please explain your issue is in as much detail as possible.
After 3.1.1 patch loaded 3.1.0 save, all banners went black.

Steps to reproduce the issue.
Load 3.1.0 save in 3.1.1?

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[MonzUn]

I have a hunch on what might be going wrong.
1. Backup and delete the contents of Documents\Paradox Interactive\Crusader Kings II\gfx\flags
2. Relaunch the game and see if it works now.
3. If it doesn't, empty that directory again and then disable your Antivirus software (or whitelist CK2) before launching the game again.