Steam Cloud Save Folder
C:\Program Files (x86)\Steam\userdata\**ID**\219990\remote\save\main

Local and Config
C:\Users\**name**\Documents\My Games\Grim Dawn\save\main

1. X32 / X64 OS
To avoid unnecessary problems, the game should be run directly from the library. Steam itself will offer launch options. Be sure to choose the X64 if it matches your system.
p. s. If you have a very old PC, below, there is specifically a mode with DX9 rendering.

2. Antivirus
As always, antivirus, the worst enemy.
I don’t have a 100% solution, but adding the executable (* .exe) to the antivirus exclusion list helped a lot. Such a white list is in each. And it’s better to add as many things as possible that are related to the process, Steam itself, including.

3. Read only
Check if the “Read Only” checkbox is on any of the folders in the save path. One has only to open the properties of the desired folder. Just in case, it’s better to force the properties on the folders, leaving the marker empty. If after this manipulation, you open the properties again, and the Read-only item is colored with a square, you should not give it more importance, we did everything we could.

If for some reason you cannot change these parameters, there are special commands for cmd, you will have to deal with this separately.

4. Check if your Documents are saved on OneDrive .
Foreword
It was just my problem, switching the read-only mode did not help. And since there were never any problems with other applications, I could not imagine that everything is so simple.
Of course, disabling the synchronization of Documents solved the problem, but this is not an option. Even using the English-language Windows 10, I did not suspect that the folder once called Cyrillic - Документи, could become an insurmountable obstacle for programmers from Crate.

Decision
- Just rename the folder in OneDrive to "Documents" [/b]
Whatever language OneDrive have named it earlier. This will not break the logic of the program.
- Deactivate the synchronization of Documents. Or, just uninstall the program if you do not need it.