This case be caused by having too many saves in your save folder or anti-virus is blocking the game from saving.

We have this noted on Discord
For anyone getting the "Not enough space" error while saving it is possibly caused by anti-virus software blocking the game's access to write saves. You need to make the game's folder an exception to the AV. Apparently this is a sure issue with the program Malwarebytes but i'm guessing it could be with others as well. i dont use any extra AV programs so i dont know how you fix it for you so cant help from here.

引用自 EmperorNiko：

This case be caused by having too many saves in your save folder or anti-virus is blocking the game from saving.

We have this noted on Discord
For anyone getting the "Not enough space" error while saving it is possibly caused by anti-virus software blocking the game's access to write saves. You need to make the game's folder an exception to the AV. Apparently this is a sure issue with the program Malwarebytes but i'm guessing it could be with others as well. i dont use any extra AV programs so i dont know how you fix it for you so cant help from here.

I have a clean game and I don't have any saves. As for the antivirus, I only have an embedded windows 10 antivirus.
Anyway, unfortunately, adding the folder to the exceptions did not help me.