It appears that there was an update to Mojave, at least that’s what came up when I clicked on “software update” a few days ago. After I did install the update, a change occurred which I don’t understand. For some reason photos I added to the Photos app by scanning them are no longer able to be displayed as desktop background. Everything was fine before this update, and I can’t seem to find out anything about why this happened. “About This Mac” still shows OS 14.6.