Intertial scrolling on mobile disabled by header scrolling

I tried to activate inertial scrolling on a (iOS) mobile device with this following custom code. This worked fine but generated another issue: if the header or tab menu on the top is touched/scrolled the scrolling of the content below is disabled for ~2 seconds.
How is it possible to prevent the header/tab menu from being scrollable?

thanks for any help!

Here is my public share link: LINK
(how to access public share link)