1. Create a Folder 'A' in resources that has sub-folder.
2. Upload files into these folders (see that sub-folder has at-least 1 file).
3. Now create new folder 'B'.
4. Copy folder 'A' and paste in folder 'B'.
5. Go to Folder 'B' and check if all the content is copied.
You will find the files in sub-folder missing.