Hambuger menu goes behind TWebPageControl

I have form with Two TWebPanels (smaller top aligned and larger client aligned) and TWebMainMenu. In larger panel is tWebPageControl. If WebMainmenu has hamburger menu on and it's enough large, it will go under TWebPageControl.
You can see behavior here https://tiedosto.skj.fi/pvm/ (press "Show Menu demo effect")
menu has tree items aa, bb, cc and each of them has 3 subitems.
Attached are that unit files.
menudemo.dfm (2.6 KB) menudemo.html (195 Bytes) menudemo.pas (1.2 KB)