Bug 449264

SUMMARY
After restarting a plasma shell with a new wallpaper, previously opened application will refresh the old wallpaper when they get the focus. This behavior is lasts a few seconds.

et your wallpaper as a slide (random few pictures)
then from konsole, restart your plasma shell: kquitapp5 plasmashell && kstart5 plasmashell
when is restarted, the plasma shell will have a different wallpaper. If you reselect the konsole window it will change the wallpaper to the previous image (before the shell restart)
if you select the desktop, the wallpaper changes again to the one from the new shell
Can't search for a ticket/raise one now (gotta go somewhere)

STEPS TO REPRODUCE
1. Set your wallaper as a slide (random few pictures)
2. Open konsole and restart your plasma shell: kquitapp5 plasmashell && kstart5 plasmashell
3. Cycle clicks between the desktop wallpaper and the opened konsole application window.

OBSERVED RESULT
1. A random wallpaper (Image 1) from the selected directory will be set for your desktop.
2. When the shell is restarted, a new wallpaper (Image 2) will be selected from the image directory.
3. When you focus the konsole window, the wallpaper for your desktop will be switched to the first wallpaper, before the shell restart (Image 1). When you click the wallpaper, the wallpaper will be switched again to Image 2.

EXPECTED RESULT
After the shell is restarted, the new image selected by the shell remains set until the timer ends or you change it manually.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Plasma master (Wayland session)
KDE Plasma Version: 5.23.90 master
KDE Frameworks Version: 5.91 master
Qt Version: 5.15.2
Video Driver: nvidia 495.46, egl-wayland 2:1.1.9

ADDITIONAL INFORMATION
This behavior lasts a few seconds.