More information is needed.
What content (video, audio, pictures) is being duplicated? What is the file format (mp3, mp4, jpg, etc.) of the file that is being duplicated?
What are you “browsing” the content of the My Cloud with? A DLNA client or Windows File Explorer or Mac Finder? If a DLNA client, what DLNA client are you using? A SmartTV? If so what model/brand?
Are there duplicate files listed when using a DLNA client like Windows Media Player?
Does Windows File Explorer or Mac Finder list multiple files?
Have you tried turning off the DLNA Media Server through the Dashboard > Settings > Media then turning it back on?
Have you looked at other threads that discuss duplicate file issues when using DLNA to see if there are any solutions in them? Here are a few of those earlier threads, there are others that can be found via a forum search:
http://community.wd.com/t/duplicate-video-files/163159
http://community.wd.com/t/video-files-appearing-twice/96571
http://community.wd.com/t/dlna-issues-on-panasonic-viera-tv-missing-and-duplicate-files/91611
Have you reviewed the Twonky FAQ to see if any of the recommendations in that thread fixes your problem?
http://community.wd.com/t/faq-twonky-dlna-media-server-setup-use/95373
