Confirmed CK III - cannot modify feudal contract, "contract already modified"

[Kosstrop]

Short summary of your issue
cannot modify feudal contract, "contract already modified"

Game Version
1.3.1

What OS are you playing on?
Windows

What platform are you using?
Steam

Do you have mods enabled?
Yes

Have you tried verifying your game files (Steam only)?
No

How much "pain" is this causing you?
(DID NOT ANSWER QUESTION)

Please explain the issue you experienced in the most condensed way possible
6

Please explain how to reproduce the issue
I was waiting for the demise of my duke vassal to remove title revocation protection he gained using weak hook on me. After the death of the duke, his heir's contract still cannot be modified.

Is there anything else you think could help us identify/replicate the issue?
I tried to modify duchy contract shortly after my new vassal inherited the title. The contract modification panel says the contract has already been modified, although I did not take any actions.

I have attached a save game
Yes

Upload Attachment
File(s) attached

 

[Earl Obelus of Brittany]

Greetings!

Thank you for bringing this matter to our attention. Our highly skilled artisans are working on it.

Godspeed!