Please use Cameyo to edit the app. Click to files and then see if there is an empty folder called C_. If yes, delete it and then try again if your "pictures" directory can be created.
Was the Pictures directory already created inside the VOS folder? Because in this case it will remain inside (isolation / full access works when creating something, not when it is already created). So if it's part of the package / its VOS directory, you'll need to create it outside the virtual repository too.