This is a known issue with numerous threads discussing it. The solution is to remove/eject the USB drive from the My Cloud. Then access the Share page within the Dashboard and remove all other Shares that were generated with the USB drive name that have the _x extension. Then reattach the USB drive to the My Cloud and rename the USB Share back to it’s initial name minus the _x extension.
Here are just a few past threads on this issue:
https://community.wd.com/t/my-safepoints-disappear/160698
https://community.wd.com/t/new-release-firmware-release-04-04-02-105-1-27-2016/148441/68
https://community.wd.com/t/mycloud-creating-numerous-aliases-for-same-drive/160161
https://community.wd.com/t/usb-drive-makes-new-name/152675
https://community.wd.com/t/dublicate-shares-after-reboot/153348
