When QWidget::move() is called in moveEvent() as following:

void Widget::moveEvent(QMoveEvent* pcEvent)
{
    this->move(0, 0);
}

That resizable widget will move to left-upper corner. (0, 0)

And if titlebar is dragged and moved, widget height is increased as attached image.

resizeEvent() is called continuously, and it can be seen increasing height here. 

void Widget::resizeEvent(QResizeEvent *event)
{
    qDebug() << "resizeEvent: old " << event->oldSize().width() << "x" <<
                event->oldSize().height();
    qDebug() << "resizeEvent: new " << event->size().width() << "x" <<
                event->size().height();
}

It's causing on CentOS 7 and Ubuntu 18.04, not causing on Windows and macOS.

Please check attached sample project.