Others have experiences similar issues with certain DLNA clients that access the Twonky media server embedded within the My Cloud. See the following two links…
https://community.wd.com/t/duplicate-files-showing-up-in-my-cloud/170197
https://community.wd.com/t/duplicate-video-files/163159
I am assuming your devices (smart TV, stereo receiver, Blue-ray disc player, etc.) that are exhibiting this problem are using DLNA to access the My Cloud. If so make sure all DLNA clients (smart TV, stereo receiver, Blue-ray disc player, etc.) are exited out of the My cloud then try rebuilding the Twonky Media Server database in the My Cloud Dashboard > Settings > Media section. If that doesn’t work access the Twonky administration page (generally http://wdmycloud:9000), navigate to the Advanced section and first select Clear Cache, then select Reset to Defaults, then select Rescan Content Folders, finally select Restart Server. Wait at least five minutes or more then recheck with the DLNA client (smart TV, stereo receiver, Blue-ray disc player, etc.) to see if the problem persists.
If the problem persists then the DLNA client may have a problem with the Media Receiver Type selected in the Twonky Administration page Sharing > Media Receivers section. Ensure the proper device is listed there for each device entry that is listed.
Further see the following link on Townky that may have some useful information.
https://community.wd.com/t/faq-twonky-dlna-media-server-setup-use/95373
