I introduced the problem to a programmer friend, who made a Windows-program based on JaceX's Python script (which I couldn't use, knowing nothing about Python and finding it too complicated for my basic common sense). I tested it briefly, and it seems to work like a charm. While waiting for the patch that fixes the problem at its root...
Ported version of JaceX python script into C# 3.5 with GUI.
Download: http://data.s.greenqloud.com/SengokuSaveFixer_0.2.rar
The program automatically takes backup of all saves it converts by renaming it into savefile.old
If you are getting an error downloading the file, try refreshing.
Program requires .Net Framework 3.5. Vista users as well as Windows 7 users should have it preinstalled.
Created by TheThing