This is Xfce added onto Ubuntu Studio 20.04.
The graphics card is GeForce GTX970 and the proprietary legacy driver v390. Which is pretty stable and has been working for years.
There are two monitors side-by-side. The problem affects both desktop areas.
Sometimes when the computer boots up, the desktop area is unresponsive: if a window is minimized an image of it stays on the screen; or if a window is moved it leaves afterimages of itself. The Xfce menus and panels all work okay, and the desktop folder opens fine in Thunar. It's just the displaying of it.
Other times, it's fine.
Having the same card I'm using the latest Nvidia 4.50.xx driver,which is compiled with the current kernel.
The driver should be the recommended one from Ubuntu's software repo.
The older 3.90.xx drivers worked better with older kernels