If you are using an old release of TSplus then you will need to update and reboot. 

If it exist please delete the c:\programdata\logon.exe

Updating your operating system is mandatory too.
You also need to update the end user's workstation graphic drivers.

Make sure you use a generated connection client with the "Disable background animation & performance". 

You can also set graphical settings in the admin tool / server tile / Groupe Policy (GPO) / adjust for best performance settings (recommended).


That being said, some application will not behave well with remote app so the only thing that you can do to help in this matter is to use standard RDP display instead.