I experienced something same yesterday.
I thought it was related to a specific loacation and while standing there near Thulla saving game and reloading, which corrupted the savegame.
In the Mycoid Camp where theres the secret Area with the reward for Sovereign Quest, you normally get 40 Exploring XP when entering that area.
You can get those XP without entering it by standing right beside DeepGnome Thulla, after she switched places when healed and is then sitting on a stone sideways of the Secret area.
So when you go near the wall to secret area besides Thulla you get 40 XP.
I quicksaved in that moment. That Savefile was then corrupted.
But i cant say for sure if its because i saved there or something else.
Anyway this corrupted savefile was my first ever in BG3
This happened after the first Hotfix for Patch 5.
Maybe its related to a bug in Hotfix 1 from Patch 5
