Help file and frame menu interfere with each other

I have a strange stacking of application + help application + frame menu (office 2010 style) - to reproduce:

 
(1) create new "TMS Office 2010 ribbon application"
(2) define event AdvToolBarPager.OnHelpClick:
  Application.HelpFile := "<full path and filename of some CHM file>";
  Application.HelpContext (0);
(3) add Vcl.HtmlHelpViewer to "uses" clause
(4) run
 
Click the Help button on the right, move the help window partially over the application window if not stacked yet. Now click the "File" menu of your application, window jumps in front of help and shows the menu.
 
Now activate the help window again, help is in front of the application skeleton, but the frame menu stays on top as if it were a splash screen.
 
Just as a note: happens with XE and XE5 (XE6 not yet tested), for latest and older component pack versions, applications I create are 32bit.
 
Thanks for looking into this! Matthias