xrandr panning with dual monitors

I would like to set up vertical panning on my laptop screen (eDP-1, native resolution 1920x1080), while using a secondary screen (HDMI-1) in its native resolution. Following [this answer](https://unix.stackexchange.com/a/217715/140232) , I have tried doing this with the following command: xrandr --output eDP-1 --panning 1920x1180 --output HDMI-1 --auto --right-of eDP-1 This gives almost the expected result, except that the vertical panning area is flickering and duplicating seemingly random parts of laptop screen rather than extending it. Without the second screen, the command xrandr --output eDP-1 --panning 1920x1180 gives exactly the expected vertical panning behaviour. What I am doing wrong? [I'm running Ubuntu 20.04 with the default desktop/window manager etc.]