As of 1/1/2017, my Time Machine backups are failing with the following message:
Time Machine couldn't complete the backup to "WDMyCloud". An error occurred while copying files. The problem may be temporary. If the problem persists, use Disk Utility to repair your backup disk.
The drive itself is a 3TB Western Digital My Cloud NAS. I can mount it in the Finder and it seems to be okay (in that I can browse it and open files), but it doesn't appear in Disk Utility at all, which doesn't seem right...
I ran the full diagnostics test in WD's utilities (it exposes a page at wdmycloud.local when the drive is powered on) and it reported no problems.
I've tried restarting both the drive and my MacBook Pro, which didn't help.
Is this a fixable problem, or is my drive dying? I'd be surprised if it's the latter, since it's less than three years old, sits untouched next to my router in a well-ventilated area, and again the diagnostics reported no issues.