SUMMARY
***
I have my wallpaper set as a slideshow that changes the image every few minutes. When I leave my computer for some time, the monitor turns off for energy saving. Later, when I wake it up, the background seems to be an image that got stuck in the middle of a transition between two wallpapers (i.e. ghosted). That is, both images are blended together.

This happens every time I leave my computer for long enough and find my screen turned off when I'm back, It's been happening for years, but never got around to reporting it, because it's not a severe thing, just an annoyance. However, it leaves Plasma in a bad place any time I come to my computer with somebody and the first thing they see is a broken wallpaper!

***
The short times proposed below are not necessary at all to reproduce the bug, just to reproduce it faster.

STEPS TO REPRODUCE
1. Set a slideshow wallpaper with a transition time of 1 minute.
2. Go to the energy saving settings and configure your screen to turn off after two minutes.
3. Wait for the screen to turn off. Then wait a couple of minutes more, to ensure that the wallpaper presentation attempts to do more transitions underneath (at least that's what I guess it's happening).
4. Wake up your screen.

OBSERVED RESULT
The background is basically two wallpapers blended together.

EXPECTED RESULT
Just one of the wallpapers of the slideshow.


Operating System: openSUSE Leap 15.4
KDE Plasma Version: 5.27.1
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Kernel Version: 5.14.21-150400.24.46-default (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Core™ i7-6600U CPU @ 2.60GHz
Memory: 7.6 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 520
Manufacturer: HP
Product Name: HP EliteBook 840 G3

ADDITIONAL INFORMATION
I get this in X11. I haven't been able to test it in Wayland, because the screen just won't turn off despite my energy saving settings.