Icons shaked in KDE Plasma task manager and system tray

Icons in task manager and system tray start to shake or blink quickly in unpredictable moments of time. Clicking on them or just switching active window stops them for some time. But in some time after some activity they start again.
Like this https :// i.postimg.cc/J7ysyP1T/trembling.gif
(look at the icons in the task manager bar at the bottom)

I used KUbuntu before on the same hardware, there was nothing similar.
What can I do about it?

> inxi -G
  Device-1: Intel WhiskeyLake-U GT2 [UHD Graphics 620] driver: i915 v: kernel
  Device-2: Cheng Uei Precision Industry (Foxlink) HP Wide Vision HD
    Integrated Webcam type: USB driver: uvcvideo
  Display: x11 server: X.Org v: 21.1.4 driver: X: loaded: modesetting
    dri: iris gpu: i915 resolution: 1920x1080~60Hz
  OpenGL: renderer: Mesa Intel UHD Graphics 620 (WHL GT2) v: 4.6 Mesa

Hi! Maybe you can attach a screenshot?

It was not a simple quest since trembling stopped when window switched, but I managed to do the video of the screen. Please find the link to animated gif in the edited original post above

That is the Icons-Only Task Manager widget and you apparently have mixed Pin applications with dragging them to it.

Set it like this:

And see if the issue persists. Remove the icons that are not Pin … Might require a log out and back in …

I have a very similar issue. After restarting it is working ok and after some time it starts shaking again.
Pay attention to the clock.
Upload video to gdrive drive. google .com/drive/folders/1zvdLcolbGHe0cy233263LTCoojB_Ufr5?usp=sharing