[danasan]

Deleting old saves should work fine as long as you don't delete them within the game but in the folder.

That means, do not start the game. Start the Windows Explorer. Navigate to the folder that contains the saves. Just delete the oldest folders there.

Start your game afterwards. It works fine for me.

If in doubt, just make a backup of the folders and put them elsewhere.

If it fails, but it does not, copy your backup back.