There is a strange error while using the fullpage script wheel event

Question

There is a strange error while using the fullpage script wheel event. When using the wheel event in the source, when section3 and section4 are reached, there is a problem that the contents shown in each section are displayed late. To return to the section when refreshing, history.pushState(null, null, "#" +currentSectionId); I used it, but it doesn't work well. Are there any errors in this source? help

function handleDisplaySize() {
var displayWidth = $(window).width();

        if (displayWidth >= 1281 && displayWidth < 1921) {
            $(window).on("wheel", wheelEventHandler);
        } else {
            $(window).off("wheel", wheelEventHandler);
            sessionStorage.removeItem("currentSectionPage");
            history.pushState(null, null, window.location.pathname);
        }
    }
    
    function wheelEventHandler(e) {
        // var lastPosTop = Number(4 * $(window).height()) - Number($(window).height());
        var lastPosTop = Number(4 * $(window).height()) - Number($(window).height() / 5);
        var scrollValue = $(document).scrollTop();
        if (mHtml.is(":animated")) return;
        if (e.originalEvent.deltaY > 0) {
            if (page == 5) return;
            page++;
        } else if (e.originalEvent.deltaY < 0) {
            if (page == 1) return;
            if(lastPosTop > scrollValue) page--;
            $("html, body").css("overflow", "hidden");
        }
        if (page == 5 && e.originalEvent.deltaY > 0) {
            var section5Top = $('#section5').offset().top - 100;
            $("html, body").animate({ scrollTop: section5Top }, 500);
        }
    
        var posTop = (page - 1) * $(window).height();
        //mHtml.animate({ scrollTop: posTop }, 500);
        //var scrollValue = $(document).scrollTop();
    
        if (page == 5) {
            $("html, body").css("overflow", "auto");
        }else{
            mHtml.animate({ scrollTop: posTop }, 500);
        }
    
        $(".section_one").each(function(index) {
            var offset = $(this).offset().top;
            var height = $(this).outerHeight();
            var top = $(document).scrollTop();
            var id = $(this).attr('id');
    
            if (top >= offset && top < offset + height) {
                $("#sidebar li").removeClass("active");
                $("#sidebar li:eq(" + index + ")").addClass("active");
                history.pushState(null, null, "#" + id);
                return false;
            }
        });
    
        updateActiveSection();
        var currentSectionId = $(".content_one .section_one").eq(page - 1).attr("id");
        sessionStorage.setItem("currentSectionPage", page);
        history.pushState(null, null, "#" + currentSectionId);
    
    }
    
    
    $("#sidebar a").on("click", function (e) {
        e.preventDefault();
        var targetSection = $(this).attr("href");
        var sectionTop = $(targetSection).offset().top;
        var isSection5 = targetSection === "#section5";
    
        $("html, body").css("overflow", isSection5 ? "auto" : "hidden");
    
        $("html, body").animate({ scrollTop: sectionTop }, 500, function() {
            if (!isSection5) {
                $("html, body").css("overflow", "hidden");
            }
            $(targetSection).siblings().removeAttr("tabindex");
            $(targetSection).attr("tabindex", 0);
            $(targetSection).focus();
        });
    
        page = $(targetSection).index() + 1;
        updateActiveSection();
        sessionStorage.setItem("currentSectionPage", page);
        history.pushState(null, null, targetSection);
    });
    
    $("#sidebar a").on("keydown", function (e) {
        if (e.key === "Enter") { // Enter 키
            e.preventDefault();
            var targetSection = $(this).attr("href");
            $(this).click();
        }
    });
    
    
    $(".section_one a , .section_one button").on("focus", function () {
        var parentSection = $(this).closest(".section_one");
        var sectionIndex = $(".section_one").index(parentSection);
        $("#sidebar li").removeClass("active");
        $("#sidebar li:eq(" + sectionIndex + ")").addClass("active");
        sessionStorage.setItem("currentSectionPage", sectionIndex + 1);
        page = sectionIndex + 1;
        var currentSectionId = parentSection.attr("id");
        history.pushState(null, null, "#" + currentSectionId);
    });
    
    
    
    function updateActiveSection() {
        $("#sidebar li").removeClass("active");
        $(".content_one .section_one").removeClass("onmove");
        $("#sidebar li").eq(page - 1).addClass("active");
        $(".content_one .section_one").eq(page - 1).addClass("onmove");
    }
    
    
    var mHtml = $("html");
    var page = 1;
    mHtml.animate({ scrollTop: 0 }, 10);
    $(window).resize(handleDisplaySize);
    
    handleDisplaySize();
    
    adjustSectionHeight();
    $(window).resize(adjustSectionHeight);
    var pageHeight = $(window).height();
    var savedPage = sessionStorage.getItem("currentSectionPage");
    if (savedPage) {
        page = parseInt(savedPage);
        var posTop = (page - 1) * $(window).height();
        mHtml.animate({ scrollTop: posTop }, 500);
        updateActiveSection();
    }
    function adjustSectionHeight() {
        var windowWidth = $(window).width();
        if (windowWidth >= 1281 && windowWidth < 1921) {
            var windowHeight = $(window).height();
            $('.section_one').css('height', windowHeight + 'px');
        } else {
            $('.section_one').css('height', 'auto');
        }
        $('#section5').css('height', 'auto');
    }
    
    $( '.search_btn button' ).click( function() {
        $( '.search_wrap' ).toggleClass( 'on' );
    } );
    
    $('.search_wrap .search_btn button').on('focusout', function() {
        $('.search_wrap').removeClass('on');
    });
    
    $('.search_wrap .keyword-btn button').on('focus', function() {
        $('.search_wrap').addClass('on');
    });