I attach the 3 pix once more, now as jpg:
When I call the page for the first time or when I refresh the homepage by clicking on the the home button, I get a correct display of the menu.
new2_menu_1st_call.jpg
Now I'm scrolling down the site, the inital menu is replaced by the menu showing up on top of the page, all correct.
news2_menu_scroll_down.jpg
When I scroll up once again, or pushing the "Back to top" link, the inital menu is not displayed anymore.
news2_menu_scroll_up_menu_missing.jpg
See screenshots
I'm using the settings "classic menu", all levels, animation on. Changing those values does not the change the descriped issue. When I switch to the overlay menu setting, it is not possible anymore to call the child menu items.