Here is what I did: I check the body y position , then make the body fixed and adjust the top to the negative of that position. On reverse, I make the body static and set the scroll to the value I recorded before.
var body_x_position = 0;
function disable_bk_scrl(){
var elb = document.querySelector('body');
body_x_position = elb.scrollTop;
// get scroll position in px
var body_x_position_m = body_x_position*(-1);
console.log(body_x_position);
document.body.style.position = "fixed";
$('body').css({ top: body_x_position_m });
}
function enable_bk_scrl(){
document.body.style.position = "static";
document.body.scrollTo(0, body_x_position);
console.log(body_x_position);
}