Sticky navigation element jumps during scroll

Question

In Firefox especially, I\'ve run into an issue I can\'t figure out how to fix.

On the following page, when scrolling down the page jumps several times - mainly on s

Answer 1

Made it this way now: Added an element before the nav:

And the jquery:

When I scroll down to 150 the placeholder gets the height of the nav, when i scroll up again I set it's height to 0.

Here is a fiddle: https://jsfiddle.net/herrfischerhamburg/562wu62y/