While user pressing burger menu its responding correctly only at the beginning of the page

Steps

1. Open a https://www.longines.com/en-us/
2. Tap “Discover” button at hero of the page (Spirit Zulu time)
3. Scroll down a page
4. Click burger menu at top left corner

Actual result

While clicking a burger menu at any position of landing page except its beginning, menu responds but doesn’t give any new options and doesn’t call a sticky footer to interact with. Problem can be solved only if user scrolls up a page a little bit.

Expected result

While user clicks burger menu it must activate pop-up footer with navigation bar