dockable widgets (in mainwindow) with common shortcut not working

[h123]

Hi,
It seems that if more than one dockwidgets are shown in main window then the shortcut set for the dockwidget's pushbutton is not working.
Pl. find the attached dockwidgets.tar.gz qt-example program, here I have attached "Esc" key to close button of both 'Customers' and 'Paragraphs' dockwidgets.
Here I want to dismiss the docked widget when I press the "Esc" key. This is working fine if one dock widget is shown (and also when dock widgets are undocked from the mainwindow) but fails if two dockwidgets are shown in mainwindow.
Thank you.