Window cursor shape randomly reverts to Qt::ArrowShape when alt-tabbing

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickItem>
#include <QQuickWindow>

class CustomItem : public QQuickItem
{
    Q_OBJECT

public:
    CustomItem() :
        mContainsMouse(false)
    {
        setAcceptedMouseButtons(Qt::AllButtons);
        setAcceptHoverEvents(true);
        setFocus(true);
    }

    void updateWindowCursorShape()
    {
        window()->setCursor(QCursor(mContainsMouse ? Qt::BlankCursor : Qt::ArrowCursor));
    }

    bool containsMouse() const
    {
        return mContainsMouse;
    }

    void setContainsMouse(bool containsMouse)
    {
        qDebug() << "setContainsMouse:" << containsMouse;
        if (containsMouse == mContainsMouse)
            return;

        mContainsMouse = containsMouse;
        updateWindowCursorShape();
    }

    void mousePressEvent(QMouseEvent *event) override
    {
        qDebug() << "mousePressEvent:" << event;
        QQuickItem::mousePressEvent(event);
        setContainsMouse(true);
    }

    void mouseMoveEvent(QMouseEvent *event) override
    {
        qDebug() << "mouseMoveEvent:" << event;
        QQuickItem::mouseMoveEvent(event);
        setContainsMouse(true);
    }

    void hoverEnterEvent(QHoverEvent *event) override
    {
        qDebug() << "hoverEnterEvent:" << event;
        QQuickItem::hoverEnterEvent(event);
        setContainsMouse(true);
    }

    void hoverMoveEvent(QHoverEvent *event) override
    {
        qDebug() << "hoverMoveEvent:" << event->posF();
        QQuickItem::hoverMoveEvent(event);
        setContainsMouse(true);
    }

    void hoverLeaveEvent(QHoverEvent *event) override
    {
        qDebug() << "hoverLeaveEvent:" << event;
        QQuickItem::hoverLeaveEvent(event);
        setContainsMouse(false);
    }

    void focusInEvent(QFocusEvent *event) override
    {
        qDebug() << "focusInEvent:" << event;
        QQuickItem::focusInEvent(event);
        setContainsMouse(true);
    }

    void focusOutEvent(QFocusEvent *event) override
    {
        qDebug() << "focusOutEvent:" << event;
        QQuickItem::focusOutEvent(event);
        setContainsMouse(false);
    }

private:
    bool mContainsMouse;
};

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType<CustomItem>("App", 1, 0, "CustomItem");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

#include "main.moc"

import QtQuick 2.0
import QtQuick.Window 2.0

import App 1.0

Window {
    id: root
    width: 640
    height: 480
    visible: true

    CustomItem {
        anchors.fill: parent
    }
}