Hello, thank you for the report. Usually these are caused by UTF8 or UNICODE characters used in the folder names (for example diacritic: á é ó). Current workaround is to use plain/basic letters for folders and directories.
"D:\Projécts\Helltáker Modding\Réléásé\Helltáker" [This will throw an ERROR]
"D:\Projects\Helltaker Modding\Release\Helltaker" [This will SAVE properly]
This will be fixed in the next update but let me know if that fixed it.