I was copying some data between two NAS units (WDMyCloud, both). I usually prefer robocopy for the task, as it is faster than Explorer and I can control many things, like multithreading.

However, during this process, I hit a snafu, it was giving the error in the title. By default robocopy uses copy:dat , which copies Data, Attributes and Timestamps. (you can read all its parameters at http://ss64.com/nt/robocopy.html)

So, once you are aware of this, the fix is simple. Prior line was:

robocopy x:\ z:\ /r:1 /w:1 /e /mir

It became:

robocopy x:\ z:\ /r:1 /w:1 /e /mir /copy:dt

And voila, it works 🙂