Unsolved Frameless widget shakes during resizing

[bibasmall]

Hello! In my project I want main window to be frameless. So I've tried different approaches to make a frameless window resizable and draggable, for example based on @IMAN4K's code from this topic Make a frameless QWidget resizable with QRubberBand ?.

The problem is that the main window shakes when resized regardless of the approach — it looks especially terrible when I put a widget in the right docking area — it looks like the content near the right main window border is being repainted several times with different width during the resizing (in the case of dock widget the whole widget trembles). It shakes only when I drag left border or left corners. I checked the shaking issue in a new project and found that the objects are shaking when they are in the layout.
Is there a way to subclass layout to solve this problem? If so, what exactly should I override?

Visually the same problem here Widget "shakes" during resizing. Any solution? unsolved — but 2 years have passed, maybe something has changed since then — and my main window shakes only when it's frameless.

[bibasmall]

Any idea?
I found that I could use Qt::CustomizeWindowHint to remove shaking if it was possible to recolor that white bar on top — but Windows 10 doesn't have that option.