Within this knowledge base, you'll learn how to resolve Black Screen / An internal error has occurred / Laggy / Slow / Disconnection issues that occurs on RDP.
This is a known issue with certain versions of Windows connecting to the latest versions Windows Server, this issue has been acknowledged by Microsoft but there is no patch yet.
However the solutions below have been confirmed to fix the issue.
First Solution:
Install the RDP Application from the Windows 10 store and use that rather then the default RDP client.
Second Solution:
On the PC you're connecting from NOT the server.
Open Group Policy Editor.
Navigate to Computer Configuration > Administration Templates > Windows Components > Remote Desktop Services > Remote Desktop Connection Client.
Set the "Turn Off UDP On Client" setting to Enabled.