There is a bug that occurs in Gekokujo when you update your save file from 3.0 to 3.1: when you take a neutral fort, you can't keep it, because the game says you already have 3750.


>To fix this you need to edit the save file.

I used Mount & Blade SaveGame Editor & Converter .
After you import your save file, you need to modify the num_forts_captured (1250) from 3750 to 0, it is under the #global_variables category.

The save file editor's author claims editing num_ variables corrupts the save file, but no issues have been detected yet. (make sure do make a backup either way duh)

Wanted to leave the solution here, since I couln't find a solution anywhere else online. You may also post it on the fandom [gekokujo.fandom.com] page, but I don't have an account for it.

Enjoy :)