[qualiteam]

This will make the header non-sticky:

#header-area .desktop-header.affix {
  position: relative;
}

But when you scroll the page down the header resizes, and there are several CSS rules that update styles depending on whether the "#header-area .desktop-header" element has the "affix" CSS class, or the "affix-top" one. You will have to find styles that would revert this behaviour, or create a custom module that will replace the "skins/crisp_white/customer/js/header.js" file with another one that won't enable the "affix" plugin on the page.