windows - RoboCopy unable to copy between a server on a domain to a computer in a workgroup

I have a RoboCopy problem and here is the scenario.

My server is running Windows Server Essentials 2012 R2. My laptop is running Windows 10 Technical Preview. The server is running as a domain controller but my computer is not joined to that domain.

I have a share on the server called "Pictures", so it's located at ~ \\192.168.1.10\Pictures which I have mapped as P: using an account tha thas Full Control privileges on that folder. I've been trying to mirror that folder to my local machine using the simple command:

RoboCopy P:\ "C:\Users\[MyUsername]\Pictures" /MIR

This always returns the error ERROR 5 (0x00000005) Accessing Destination Directory even though the destination directory is under my user account where I am the owner. I have tried using both an administrative command prompt as well as the standard user command prompt. Neither works :(

Using RoboCopy between two local folders using the Pictures folder as a destination works just fine, so I'm guessing this has something to do with domain permissions rather than the actual destination permissions.

P.S.

The funny thing is this worked just fine when my computer was using Windows 8 and connected to the Server Essentials using the Connector application without domain joining (The Connector app isn't available for Windows 10).

P.P.S

Copying directly in Windows Explorer works just fine, but I need RoboCopy since it's much more efficient at syncing large folders.

Any help would be appreciated.

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Update

I am unable to try with a local user on the server since the server is a domain controller. I did however try to give the domain user I use to map the network drive on the workgroup machine full permissions on the folder as well as making him owner and still no dice. Here is the exact RoboCopy output:

-------------------------------------------------------------------------------
   ROBOCOPY     ::     Robust File Copy for Windows
-------------------------------------------------------------------------------
  Started : fimmtudagur, 25. júní 2015 21:40:01
   Source : P:\
     Dest : C:\Users\stefa\OneDrive\Pictures\
    Files : *.*
  Options : *.* /V /S /DCOPY:DA /COPY:DAT /R:1000000 /W:30
------------------------------------------------------------------------------
                      25    P:\
2015/06/25 21:40:02 ERROR 67 (0x00000043) Accessing Destination Directory C:\Users\stefa\OneDrive\Pictures\
The network name cannot be found.
Waiting 30 seconds...

Update 2
I'm fairly certain I have just hit a bug in Windows 10 (still there in 10159). When I try this on a Windows 8.1 machine (x64 as well as RT, clean install on both) by using robocopy over a mapped network drive or net use \\192.168.1.10\IPC$ ... everything works just fine. But using a Windows 10 client, this does not work. My theory is that either something is has broken in the way Robocopy does network copies in Windows 10 or something in the network stack in Windows 10 has broken RoboCopy.