Windows: deleteLater() invoked from ActiveX callback/slot doesn't delete until the application terminates

As described at https://forum.qt.io/topic/15042/deletelater-from-within-activex-event-handler :

1. Take the webbrowser example.
2. Add a new class:

   class QExample : public QObject
   {
   public:
   	bool event(QEvent* e) override
   	{
   		if (e->type() == QEvent::DeferredDelete)
   			QMessageBox::information(0, "1", "DeferredDelete");
   		return QObject::event(e);
   	}
   };

3. Add it to MainWindow:

   class MainWindow : public QMainWindow, public Ui::MainWindow
   {
   	...
   	QExample* ex;
   };

4. Create it:

   MainWindow::MainWindow()
   {
   	ex = new QExample;
   	...
   }

5. Request its deletion:

   void MainWindow::on_WebBrowser_NavigateComplete(const QString &url)
   {
   	ex->deleteLater();
   	...
   }

The example object is expected to be deleted when the execution returns to the event loop, but it only happens when the browser is closed.

A little background. I have an application that can be run both as a standalone executable and an ActiveX server. In the first mode, all is fine, but deleteLater()s don't properly work in the latter, the deferred-deleted objects basically leak during the application lifetime.