Twitch block position: fixed; when scrolling in ios?

Question

JavaScript

In the mobile version, it is done so that when scrolling up, the menu is fixed at the top and, accordingly, when scrolling down, it is removed. Scrolling is done to a certain anchor at the bottom and the problem is that in the mobile version on ios, when you change fixed to relative at the anchor, the block twitches. This is especially noticeable in ios . How to get rid of this effect?