Sticky Header Jumps on iOS

[StefanImhoff]

Hi,

I use sticky.js to fix the header of a client site. When fixed, some elements are hidden. so the header shriks.
In the header is a searchbox.
So, now the issue:
When I click on a iPhone/Chrome in the non-sticky header-searchbox, the page scrolls to keep the searchbox in viewport, the header gets sticky and shrinks. then the keyboard is appears. For unknown reasons the complete viewport seems to be pushed upward, so the sticky header is scolling out of the viewport.
As I red, this theems to be an issue with iOS.
I found this solution:
https://stackoverflow.com/questions/14492613/ios-ipad-fixed-position-breaks-when-keyboard-is-opened

It works fine, if the header is sticky before. But with the shrinking header on intial view/clicking in searchbox, it does not work.

How can I fix this?

Best regards!