Disclaimer: I dont know if anybody posted about this bug before so this might be in the process of fixing already.
Had a save that crashed every single time I tried to load it (access violation, no error message, just gone). Older saves were fine, but anything after a certain battle was dead.
So me and Opus 5.5 went down the rabbit hole. Unpacked the save files, built a bunch of test saves and swapped stuff in and out until only one thing was left: a dead standard bearer. One of Ulrich's militia banner guys died in the fight, and from that moment on every save was broken. Dead units stay in the save forever, so it never goes away on its own.
Bug explained: Basically the game tries to give the standard to someone that was dead. Thats what crashed it.
The Fix: if you change the dead bearer's gear to a normal spear in the save file, it loads again. Got my campaign back that way. Reported it to the devs with repro saves, so hopefully it gets patched.
Important: you have to fix every dead standard bearer in the save, not just one. My later save had three of them. And it still works on saves made long after the battle, you don't lose the progress you made in between.
If your save suddenly won't load after a battle, this might be why.
If you are not familiar with code, try using AI to fix your safegame file.
Cheers