I have a single file in a directory "Earth.jpg" which is an image of the GOES full disk color image of the earth. It is fetched from a script every 10 minutes. The file name never changes and it's the only file in that directory.
The issue is that setting "Configure Desktop -> Wallpaper" settings using either the "slideshow" wallpaper type or "Image" does not update the background wallpaper. It updates the background once and then stops re-reading the image file again, even if using the Slideshow setting and telling it to change every minute.

The odd thing is that the image thumbnail preview below the settings panel updates to the actual image in the directory as it should. So thumbnail previews in "Configure Desktop -> Wallpaper" work like the background should work. So the code is written properly for the thumbnail image preview it just doesnt seem to apply to the code to refresh the actual desktop image.


STEPS TO REPRODUCE
1. Fetch an image every n minutes that changes each time it's fetched and put it in a directory with a filename that does not change and is the only file in the directory.
2. Go to "Configure Desktop" from the contextual menu by right clicking on the desktop.
3. Go to Wallpaper
4. Select Image or Slide show, for slideshow select update every 5 seconds for testing purposes.
5. Select the directory your image that updates is locate in and select the image.

OBSERVED RESULT

6. Watch the thumbnail below the settings update every 5 seconds but the actual background image does not change from the initial fetch of the image.

EXPECTED RESULT

7. The background image should update by rescanning the directory and image file you selected to update the background even if the filename does not change or if there is only one image in the wallpaper directory chosen. 

SOFTWARE/OS VERSIONS
FreeBSD: 12.1 Release


KDE Plasma Version: 5.16.5 
KDE Frameworks Version: 5.62.0
Qt Version: 5.13.0

ADDITIONAL INFORMATION
Hardware: 
Processors: 4 x ACPI CPU
Memory: 8GB