Listview scrollbar changes size and jumps

import QtQuick
import QtQuick.Controls

ApplicationWindow
{
    id: mainWindow

    visible: true
    width: 1600
    height: 1070

    Component.onCompleted:
    {
        for (let i = 0; i < 100; i++)
        {
             var data = {'name': new Date().toTimeString(), 'itemHeight': Math.random()*1000};
            fruitModel.append(data)
        }
    }

    ListModel
    {
        id: fruitModel
    }

    ListView
    {
        id: listView
        anchors.fill: parent
        spacing: 2
        model: fruitModel
        ScrollBar.vertical: ScrollBar
        {
        }

        delegate: Rectangle
        {
            height: itemHeight
            width: listView.width
            Text { text: name }
            color: Qt.rgba(Math.random(),Math.random(),Math.random(),1);
        }
    }

}