I just ran into this problem yesterday. Turns out I had to turn Windows10 Defender Anti-Ransomware off. Definitely not a fix, but at least I can save games again. I did try leaving anti-ransomware on and allowing the apps for steam and Bannerlord2 to be exceptions, but game still would not save. I’m currently using 1.3.0.Beta, but had the same issue when trying to revert back to earlier betas and the mainstream versions. Also tried reinstalling game on several different drives. And even uninstalled/reinstalled Steam. Other games on Steam platform were able to save prior to turning anti-ransomware off.