저도 loop함수만 실행하면 오류가떠요!

안녕하세요! 저도 스크립트에서 loop(); 만 실행하면

스크롤 하게되면

강아지있는 사진이 붕 뜨는데 뭐가 문제일까요ㅠㅠ

혹시 코드 봐주실수 있나요!!

let x = 0;
let y = 0;
let mx = 0;
let my = 0;
let speed = 0.03;
let scrollTop = 0;

let parallax_0, parallax_1, parallax_2, parallax_3, parallax_4, parallax_5, parallax_6;

window.onload = function () {
progressBar = document.getElementsByClassName("progressBar")[0];

parallax_0 = document.getElementById("parallax_0");
parallax_1 = document.getElementById("parallax_1");
parallax_2 = document.getElementById("parallax_2");
parallax_3 = document.getElementById("parallax_3");
parallax_4 = document.getElementById("parallax_4");
parallax_5 = document.getElementById("parallax_5");
parallax_6 = document.getElementById("parallax_6");

window.addEventListener('resize', stageResize, false);
window.addEventListener('mousemove', mouseMove, false);
window.addEventListener('scroll', scrollFunc, false);

stageResize();
loop();
}

function scrollFunc(e) {
scrollTop = document.documentElement.scrollTop;

let per = Math.ceil(scrollTop / (_documentHum - _windowHNum) * 100);
progressBar.style.width = per + '%';

parallax_0.style.transform = "translate3d(0px," + scrollTop * .03 + "px, 0px)";
parallax_1.style.transform = "translate3d(0px," + -scrollTop * .03 + "px, 0px)";
parallax_2.style.transform = "translate3d(0px," + -scrollTop * .12 + "px, 0px)";
parallax_3.style.transform = "translate3d(0px," + -scrollTop * .16 + "px, 0px)";
parallax_4.style.transform = "translate3d(0px," + -scrollTop * .22 + "px, 0px)";
parallax_5.style.transform = "translate3d(0px," + -scrollTop * .25 + "px, 0px)";
}

function stageResize(){
_documentHum = document.body.offsetHeight;
_windowHNum = window.outerHeight;
}

function loop(){
mx += (x - mx) * speed;
my += (y - my) * speed;

parallax_4.style.transform = "translate3d(" + mx / 140 + "px ," + -scrollTop * 22 + "px, 0px)";
parallax_5.style.transform = "scale(1.1) translate(" + mx / 50 + "px," + -scrollTop * 25 + "px)";
parallax_6.style.transform = "scale(1.2) translate(" + -mx / 20 + "px," + -my / 20 + "px)";

window.requestAnimationFrame(loop);
}

function mouseMove(e){

x = (e.clientX - window.innerWidth / 2);
y = (e.clientY - window.innerHeight / 2);
}

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