Remote Desktop event ID 20499. No noticeable issues

Solution 1:

This will solve your problem:

In Registry Editor, locate and then click one of the following registry subkeys:

HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows NT\Terminal Services

Add DWORD fQueryUserConfigFromLocalMachine with value 1

restart

Reference https://support.microsoft.com/nl-nl/help/4021856/sbsl-issue-when-you-create-an-rdp-connection-to-windows-server

Solution 2:

Apparently this can be triggered by using mRemote / Remote Desktop Connection Manager (RCDMan 2.2) or similar software.

The fix is to set TaskOffload = Disabled using Set-NetOffloadGlobalSetting

Source: http://www.itnotes.eu/?p=1193