Problem with scrolling at the top and the bottom of the page


We created a website for web flow and we have a problem - when we scroll the site to the top or at the bottom of the page, the site gets jerky, for example on this site - or this -

Here is a gif with this -

This trouble occurs in Safari 7 on mac

Gif is not visible + websites are totally fine for me. Could you please be more specific?

Here is video from youtube - - YouTube

In both cases i just scrolled down one time