Sticky header jumps when scrolling

I have sticky enabled for the header. In non-sticky mode, the header is 80px tall; in stick mode, 60px. When one scrolls down, the header jumps and shrinks to its sticky height. I don’t want the header to jump anymore.

I’ve experimented with setting the height of sticky and non-sticky to be the same, but that does not help. How do I get this jumping to stop happening when people scroll down the page?

The website in question: http://www.camiros.com

Thank you.