We have a new Windows Servers 2012R2 RDS server Farm comprising a number of Physical Windows 2012R2 servers and Virtual Windows 2012R2 servers. Shadowing fails with the wonderfully helpful error 'Shadow Error Unspecified Error' when trying to shadow user sessions on the Physical server(s) only. The problem occurs when shadowing from the Server Manager console / command line and PowerShell. No errors appear in any logs when trying to make the Shadow connection.

The problem is temporarily cured by a server reboot then returns the next day (appears as if some process runs on the servers overnight and induces the issue)

The Virtual Server(s) with identical Software Configuration in terms of installed applications and configuration are unaffected by the issue. The affected Physical Servers in use are all new HP Proliant DL360 G9's with latest firmware and drivers as provided by HP.

We have completely rebuilt one of the servers from scratch with a clean install of Windows 2012R2 etc including all latest patches via Windows Update and the problem persists. There are no issues with user sessions - everything else is working fine within the environment with the exception of the Session Shadowing which is used by the administrators on a regular basis.

Any assistance would be greatly appreciated..

Hi,
To better troubleshoot the issue, I suggest you start Process Monitor, then try to shadow session with Server Manager console / command line and PowerShell to re-produce the issue. After that, stop Process Monitor capture to analyze thread activityies.

Process Monitor v3.2
https://technet.microsoft.com/en-us/library/bb896645.aspx?f=255&MSPPError=-2147217396

Best Regards,
Amy