Firefox and IE JS scrolling issue

Question

On this page http://eisenpar.com/chocolate/index-free.html I've tried to create an effect: if you are at the top of the page and make a scroll, page scrolls on the window height and a fixed navigation appears. It works properly in Chrome, Opera and Edge (I haven't tested in Safari yet), but in Firefox and IE11 this effect crashes: it scrolls to bottom and then - to the top without any pause. In IE it shows navigation, in FF it doesn't, just sends me to the top of the page.

Here is my script for this effect:

var scrollBool = false;

jQuery(window).scroll(function() {

   var winHeight = window.innerHeight;
       navHeight = jQuery('nav').outerHeight();

    if (scrollBool == false) {

      scrollBool = true;

      if(jQuery('nav').hasClass('fixed')) {

        if (jQuery('body').scrollTop() + 10 < winHeight) {

          jQuery('nav').removeClass('fixed');

          jQuery("html, body").stop().animate({
            scrollTop: jQuery('header').offset().top
          }, 700, function() {
            scrollBool = false;
          }); 

        } else {
          scrollBool = false;
        }

      } else {

        if (jQuery('body').scrollTop() < winHeight) {

          if(jQuery('nav a, .link-block a').hasClass('in-scroll')) {

          } else {
            jQuery("html, body").stop().animate({
              scrollTop: jQuery('header').offset().top + winHeight
            }, 700, function() {
              scrollBool = false;
              jQuery('nav').addClass('fixed');

            }); 
          }
        } else {
          scrollBool = false;
        }
      }
    }

});

Answer 1

Finally - fixed. FF has issues with jQuery('body').scrollTop() , it doesn't understand it properly, everything is fixed if I change this to jQuery(window).scrollTop()