Cannot receive dragLeave/dragMove events until dragEnter is accpeted on QTabWidget/QTabBar

QExtTabWidget::QExtTabWidget(QWidget *parent)
 : QTabWidget(parent)
{
 // Need to set acceptdrops for tabBar explicitely, else dragEnter event is never sent
 // to the tabBar itself but only to owning QTabWidget. This leads to the problem that
 // dragEnter event is not sent as when the cursor has been already in the tab widget.
 // So dragging something from inside the tab widget (e.g. from a client widget) to the tab widget's
 // tabbar triggers no dragEnter event.
 this->tabBar()->setAcceptDrops(true);

 // install event filter to intercept events sent to this widgets tabbar
 this->tabBar()->installEventFilter(this);
}

bool QExtTabWidget::eventFilter( QObject *target, QEvent *event)
{
 if ( !(target == this->tabBar()) )
   return false;

 if (event->type() == QEvent::DragEnter)
 {
  // need to accept the event, else QEvent::DragLeave and QEvent::DragMove won't be trigggered on the tabBar widget
  // and the code for dragMove and dragLeave below is never called

  QDragEnterEvent *dragEnterEvent = dynamic_cast<QDragEnterEvent*>(event);
  Q_ASSERT(dragEnterEvent != nullptr);

  // comment next line out to reproduce the issue
  dragEnterEvent->accept();

  qDebug() << event->type();
  return false;
 }
 else if ((event->type() == QEvent::DragLeave) || (event->type() == QEvent::Drop))
 {
  qDebug() << event->type();
  return false;
 }
 else if (event->type() == QEvent::DragMove)
 {
  qDebug() << event->type();
  return false;
 }

 return false;
}