I believe that its a problem with the english patch. If you put the old data files back in, then it should work fine.
This solved it, thank you!
I encountered the same problem and just played that chapter in Japanese. Apparently you can't load a quick save from the English version with the Japanese one (and vice versa), so you ought to play the entire chapter in Japanese.
You can put the patched files back after you properly saved the game.
I put the Japanese version data folder on the English installation, changing the English data folder name, in which I had a quicksave one turn away from winning. The only thing I had to do was passing the turn, saving the game and change the names of the folders back. It's a solution a bit heavy, as it takes half a giga of space, but this way If I want to replay the game I can pass through this part with the minimum effort.