QTitanRibbon 7: RibbonGroup::addAction does not work from Qt slot

#include <QApplication>
#include <QGroupBox>
#include <QToolButton>
#include <QVBoxLayout>

#include <QtitanRibbon.h>
#include <QtnRibbonMainWindow.h>

class MainWindow : public RibbonMainWindow
{
  Q_OBJECT

 public:
  MainWindow()
      : RibbonMainWindow()
  {
    auto groupBox = new QGroupBox( "Test", this );

    auto button1 = new QToolButton( this );
    button1->setText( "Add button to Ribbon" );

    connect( button1, &QToolButton::clicked, this, [ this ]() {
      RibbonGroup* group = ribbonBar()->page( 0 )->addGroup( "New Group" );

      auto action2 = new QAction( "Button2", this );
      connect( action2, &QAction::triggered, this, []() { qDebug() << "Button2"; } );
      group->addAction( action2, Qt::ToolButtonTextUnderIcon );
    } );

    auto vLayout = new QVBoxLayout;
    vLayout->addWidget( button1 );

    groupBox->setLayout( vLayout );

    setCentralWidget( groupBox );

    {
      auto page = ribbonBar()->addPage( tr( "Page1" ) );
      RibbonGroup* group1 = page->addGroup( tr( "Group1" ) );
      ribbonBar()->setFrameThemeEnabled( true );

      auto action1 = new QAction( "Button1", this );
      connect( action1, &QAction::triggered, this, []() { qDebug() << "Button1"; } );
      group1->addAction( action1, Qt::ToolButtonTextUnderIcon );
    }

    setWindowTitle( tr( "MissingButton Test" ) );
  }
};

int main( int argc, char* argv[] )
{
  QApplication app( argc, argv );
  MainWindow mw;
  mw.resize( 640, 480 );
  mw.show();
  return app.exec();
}

#include "main.moc"