Broken rendering when reparenting WebEngineView to another window

Compositor returned null texture

import QtQuick
import QtQuick.Controls
import QtWebEngine

Window {
    id: mainWindow
    width: 300
    height: 300
    title: 'Main '
    visible: true

    WebEngineView {
        id: webView
        anchors.fill: parent
        url: 'https://www.qt.io/blog'
    }

    Window {
        id: childWindow
        width: mainWindow.width
        height: mainWindow.height
        x: mainWindow.x + mainWindow.width
        y: mainWindow.y
        title: 'Child'
        visible: true
    }

    Button {
        z: 1000
        text: (webView.parent === mainWindow.contentItem) ? 'To Child' : 'To Main'
        onClicked: {
            if (webView.parent === mainWindow.contentItem)
                webView.parent = childWindow.contentItem
            else
                webView.parent = mainWindow.contentItem
        }
    }
}