I was having this strange issue that whenever I attempted an RDP connection to a new server install, it would connect then immediately disconnect.
Windows was completely up to date and nothing had even been installed on the server.
Turns out its the RDPCoreKMTS.dll file.
An error was logged in the event log that got me here.
To resolve this, I simply replaced the dll with a known good dll from another server:
1) Get on affected computer’s console.
2) Stop the Remote Desktop Services.
3) Take Ownership of file C:\Windows\System32\rdpcorekmts.dll and assign full NTFS permissions to your account.
4) Rename file to rdpcorekmts.old
5) Copy file rdpcorekmts.dll from another server.
6) Start the Remote Desktop Services.