QtitanDocking 2.3.0+QtitanRibbon 5.0.0: showDockPanel does not show docked panel

The code below should show or hide dockPanel1 if button "Button" is pressed.
If dockPanel1 is floating this works. But if dockPanel1 is docked the panel could be hidden but not shown again.

:h
#pragma once

#include <QtitanRibbon.h>
#include <QtitanDocking.h>


class GuiTest : public RibbonMainWindow
{
Q_OBJECT

public:
GuiTest(QWidget *parent = Q_NULLPTR);

private:
Ui::GuiTest ui;
DockPanelManager *dockPanelManager;
DockWidgetPanel* dockPanel1;
QAction *TestAct;

public slots:
void panelActionTriggered();

};


:cpp

#include <QtitanRibbon.h>
#include <QtitanDocking.h>

GuiTest::GuiTest(QWidget *parent)
: RibbonMainWindow(parent)
{
QLatin1String m_defaultStyle("windowsvista");
qApp->style()->setObjectName(m_defaultStyle);

ui.setupUi(this);

setWindowTitle("QtitanRibbon + QtitanDocking");

ribbonBar()->setFrameThemeEnabled(true);
ribbonBar()->setTitleBarVisible(true);

QWidget *widget = new QWidget;
dockPanelManager = new DockPanelManager(widget);
dockPanelManager->setDockPanelTransparentWhileDragging(true);
dockPanelManager->setArrowMarkersShown(true);
dockPanelManager->setDockPanelFullContentsWhileDraggingShown(true);
setCentralWidget(widget);

////// 2 - Creating a ribbon
ribbonBar()->setFrameThemeEnabled();
RibbonPage *page = ribbonBar()->addPage("&Buttons1");

////// 3 - Creating a dockBarManager
DockBarManager* managerBar = new DockBarManager(widget);
DockToolBar* tooBar = managerBar->addToolBar("My Toolbar", Qtitan::DockBarTop);
TestAct = tooBar->addAction("Button");
TestAct->setCheckable(true);
TestAct->setChecked(true);
connect(TestAct, SIGNAL(triggered()), this, SLOT(panelActionTriggered()));

////// 4 - Creating a panelManager
dockPanel1 = dockPanelManager->addDockPanel("My Panel_1", Qtitan::LeftDockPanelArea);
dockPanel1->setWidget(new QLabel("panel1"));
DockWidgetPanel* dockPanel2 = dockPanelManager->addDockPanel("My Panel_2", Qtitan::RightDockPanelArea);
dockPanel2->setWidget(new QLabel("panel2"));
}

void GuiTest::panelActionTriggered()
{
if (TestAct->isChecked())
dockPanelManager->showDockPanel(dockPanel1);
else
dockPanel1->closePanel();
}

Hello!
We’ve used your source code to reproduce the error of QtitanRibbon 5.3.1 and QtitanDocking 3.1.0 versions. But we didn’t succeed. Please, update these components. To see it clear to you, we send you gif file.