Since purchasing My Cloud Mirror, I had much difficulty with copying files from my laptop. I would consistently get “Error 0x8007003b - an unexpected network error occurred” using Windows 10. I also received a similar error on Windows 7 (same laptop, dual boot). To find out if it was my laptop or My Cloud, I copied the same folder (~7GB of photos in RAW format) to another PC in my house. It worked every time, so it must be My Cloud. After much research I didn’t find a solution, so I decided to poke around the My Cloud dashboard. I decided to turn off Oplocks on the share I was copying to. Happy to say that worked! My throughput is much higher too - ~10 MB/s. I don’t know if WD’s implementation of Oplocks is broke, but since I’m the only one who uses the share, I didn’t see a need for it anyway.
Hope this helps anyone who is having the same problem!
PS - I’m on the firmware 2.10.310