Created attachment 140970 [details]
video with a reproducible effect

The system starts to lag when playing an animation, for example, when switching wallpapers on the desktop.

I use the latest NVIDIA video driver. The problem also appears on earlier versions of the driver. The kernel does not affect the result.

The problem persists when using rendering backend: OpenGL 2.0/3.0 and XRender.

CPU, GPU, and RAM are not loaded.

I used to use the LTS version of kde 5.12 , there was no such problem.

The easiest way to get the effect
STEPS TO REPRODUCE
1. Turn the game on in full-screen mode and turn it off
2. Try changing the wallpaper.

The effect also manifests itself if you put the system into sleep mode and wake it up. But not significantly.

Also, the effect may appear after a long time.

There is also a slowdown when performing various tasks, I will not say exactly what, but sometimes it is visible.

OBSERVED RESULT

Complete slowing down of all observed windows and animations
Small FPS when playing an animation and not only.


EXPECTED RESULT
Remove this bug.


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE tumbleweed 
(available in About System)
KDE Plasma Version: 5.22.4
KDE Frameworks Version: 5.85.0
Qt Version: 5.15.2
Graphics Platform: X11


ADDITIONAL INFORMATION
CPU: Intel Core i5 9400f
RAM: 32Gb
GPU: NVIDIA GeForce GTX 1660 Super
Nvidia Driver: 470.57.02

and for clarity, I attached a video.