Created attachment 6481
Workspace settings dialog
Large blocks of the screen are suddenly redrawn with corresponding areas of some other workspace.
Performing some action which causes the current workspace to redraw remedies the problem until the next occurrence.
Not sure what I am supposed to see i nthe screenshot, it looks fine to me.
But from whta you describe, it looks like a driver issue, what X11 driver do you use, and which version of the X11 server?
Do you have the compositor enabled? What if you disable it?
I was having the exact same problem, with increasing frequency. It did show some correlation with which applications are open, e.g. closing Chrome could make it somewhat, but not entirely, better. This is with Ubuntu 16.04.5, and XFCE 4.12.2 as Ubuntu installs it.
Disabling the compositor, then replacing it with compton (from https://launchpad.net/~kelleyk/+archive/ubuntu/compton ppa) fully fixed it. This is with the radeon module loaded, for a Radeon HD 6450 1 GB DDR3 graphics card.
The compton compositor also seems snappier.
Also, that's with x11-common 1:7.7+13ubuntu3.1.
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