I have a very strange issue that I never faced before but I'll give you the full story in order for you to fully understand the network/computer setup and the issue that is occuring.
The company WG has two sites which are connected through a permanent Fortinet VPN Tunnel which is working fine.
No Real Windows servers are used on any of the sites and the dhcp and dns are handled by the Fortinets
A small Synology serves as storage unit for the files and folders and a desktop computer serves as a CRM server (not safe I know ;-) )
The computers on one site are connecting on computers on the other side in order to get access tothe CRM using remote desktop connections
Everything is working well for 1 to 2 years till a month ago on a new computer (the computer of the boss of course, murphy's law is there to please us)
On this computer (a new Intel NUC with Win 8.1 Pro ), when you are launching a remote connection to the computer of the boss on the other site (a Lenovo with Win 8.1 Pro), it connect perfectly but there is a "small" quality issue as you may notice in the attached pictures.
As you may see, it is not related to a specific application and it only appear on a remote connection, everything is ok on the computer locally
When you are making snapshot on the remote computer, the snapshot are clean without any strange thing
When you connect to the same remote computer from another computer on the same network than the affected system, you haven't the display issue
I Tried to change the connection and go from the Wireless connection to a cable connection, no change at all
I tried to change the color and display settings in the remote client, no change
I tried to install the latest firmware, bios and drivers on both computers, no change
I installed all the updates and the .net framework 3.5, no change
I tried to uninstall the graphic card, reboot and reinstall it, no change
I made a full reset of the network settings with the 4 netsh commands and still no change after reboot
I tried with another wireless card, no change
I tried with a single screen instead of the two present, no change
I tried reboot the destination computer, no change
I tried to use the remote connection manager instead of the remote client, no change
I'm at a loss and any idea is very welcome...