there is a bug in wallpapers. i set my own per monitors, then had to reboot because of updates, and they were back to the default ones. though, when i went in to change them again its like the system still thought they were set to the ones i changed them to because i would have to go selected a different wallpaper and apply that one, then go back and select the one i really wanted. also the wallpaper(s) i was selecting from disk that showed up in the window would disappear after the reboot as well.

as you can see here the image i want to use and applied: https://i.imgur.com/ftAdn3h.png

and then after a reboot: https://i.imgur.com/iH6TuAu.png

its like the images i added are there but not in the desktop folder settings window after reboot.