Sometimes when I try to open, close, or select items in "Settings" (gnome-control-panel), Ubuntu becomes mostly-unusable. I cannot change which window is active, or minimize windows, for instance, though things continue to scroll by in active windows, audio continues to play. This lasts for a few minutes. Sometimes I get the "Settings is not responding" dialog; sometimes not. If I do, selecting "Force Quit" or "Wait" usually sends the system back into its unusable / semi-locked state.

I tried starting the control panel with `gnome-control-panel --verbose`.

I see a seemingly endless set of "DEBUG: Adding device (null)..." / "Saving device type Unknown for..." messages during these lock-up periods. They just go on and on.

Any advice for me?

Ubuntu 20.04.1 / Gnome 3.36.8