I was going to say that is probably the cause but then I saw this post:
But it might be worthwhile at least trying to force the resolution to 30Hz (since it would be pushing 50% less data about), which might double the responsiveness. I guess that the first step would be to check if your monitor actually supports 1920x1080 at 30Hz
And maybe there is a gnome option to select a new frame rate.
gnome → settings → displays
But since you installed XFCE, you are on your own. Because you might have overwritten some of the critical files with newer versions but with less functionality for the VF2 board in the process.
I do not suppose that you safeguarded against that ?