Update to 22.04 from MATE on 21.10 and now my background is all messed up

I just updated from 21.10 -> 22.04. I was using MATE and had run a script (impishgdm) to set the gdm3 login screen. Then I updated. Not sure if impishgdm caused this but after updating to 22.04, when I log in, a large portion of my screen is all white and a tiny portion at the bottom is showing the true wallpaper. In the attached image you'll see the green grass blades of the wallpaper. But the top portion is all white (and the screen capture captures it as black - strange!). If I change the wallpaper only the bottom portion changes. How can I fix this?