I have Windows 11, but the problem was also found on Windows 10.

This can be reproduced only on some display. The one I use to reproduce it is: 'Intel(R) Iris(R) Xe Graphics', 1920 * 1080, 60Hz.

I have modified the 'Minimal' WebEngine example, by just adding a Rectangle at the left side of the WebEngineView:

import QtQuick
import QtQuick.Window
import QtWebEngine

Window {
    width: 500
    height: 300
    visible: true


    Rectangle
    {
        id: extraRect
        height: parent.height
        width: 10
    }

    WebEngineView
    {
        anchors.left: extraRect.right
        height: parent.height
        width: parent.width - extraRect.width

        url: "file:///C:/Users/me/Downloads/debug.html"
    }
}

In the attachment you can see the difference between the 'Minimal' application, and what I see when opening the html file directly with Chrome.
If I change the width of the Application Window, then I see the letters flickering, sometimes some letters are then rendered in the right way, sometimes, they are again cut, or having a red or green pixel.
What makes it quite strange, is that if I remove the 'extraRect', or set its width to 0, then the rendering is then OK, and I don't get this flickering when changing the width of the window.

I can reproduce with Qt 6.4, but not with Qt 5.