I recently connected a Windows Server 2012 R2 computer to my existing Remote Desktop Manager v2.7 console.
When I tried to adjust the screen size to scale to the remote desktop to fit the window the display was distorted.
To fix this I had to close my Remote Desktop Connection Manager and clear the bitmap cache on my local computer NOT the Remote Server.
To do this I deleted the file in the following directory:-
C:\Users\%UserName%\AppData\Local\Microsoft\Terminal Server Client\Cache
This fixed the issue