Sorry, it was only now that I read the known issues.
By the way, where is the game's savegame? I am using Windows 11.
I posted a couple of save bug logs in the Discord bug-reports section.
To repeat it, just start the game, try to save (a message saying it was not possible to save will appear) and it fails. Go to Dealership -> Restock -> Play -> Save and it will be saved normally.
In fact, this also happens when I collect without restocking the dealership and try to save.