Update: I copied my savegames back to the Linux machine and there it is still working. But I want to play on my big screen running windows. I watched the Malutina sequence and saved when I got free the next morning and moved the savefiles back to windows, hoping a crash won't happen again. I kept playing for a while, but when I want to confront Zhara in the town hall the game crashes again (same error) when I enter her room.
I have uploaded the new save folder. savefile 22 is right before Malutina city gate crash, savefile 24 is before entering the town hall crash:
https://www67.zippyshare.com/v/n6voMDr6/file.html
Would be great if you could do anything to help. I could continue playing on Linux but I want to enjoy the game on the big screen. I don't want to start from scratch on windows (because I can't even be sure if the Linux-widows-switch really is the cause of the problem, I only read in an rpgmaker forum that the "header is wrong" error could be caused by an incompatible savefile, so I assume starting on Linux and moving to windows is the cause of the problem).