Header/footer code misbehaving?

Hello, I had an issue with portions of my website (image galleries and individual images)  all of a sudden loading slowly or not at all. I had not made any recent changes. A SquareSpace customer service agent told me this was probably due to a SquareSpace update causing the header/footer code to "misbehave".  Turning off the Ajax scroll made the loading respond normally/quickly again, however, I'd like to be able to turn it back on. Has anyone had this experience? Is it possible to identify and fix the code? (I didn't write the code and don't have access to the person who did at the moment.) The agent said he doesn't know what update might have caused it. Thanks!

Can you share your website URL and the code? What is the code for?

Thank you for responding. I hope this helps.

The URL is www.menuez.com

I was told by a customer service agent that the "misbehaving" code is probably the header/footer.

The header code is

<!-- Facebook Pixel Code -->
<script>
!function(f,b,e,v,n,t,s)
{if(f.fbq)return;n=f.fbq=function(){n.callMethod?
n.callMethod.apply(n,arguments):n.queue.push(arguments)};
if(!f._fbq)f._fbq=n;n.push=n;n.loaded=!0;n.version='2.0';
n.queue=[];t=b.createElement(e);t.async=!0;
t.src=v;s=b.getElementsByTagName(e)[0];
s.parentNode.insertBefore(t,s)}(window, document,'script',
'https://connect.facebook.net/en_US/fbevents.js');
fbq('init', '254300449484735');
fbq('track', 'PageView');
</script>
<noscript><img height="1" width="1" style="display:none"
src="https://www.facebook.com/tr?id=254300449484735&ev=PageView&noscript=1"
/></noscript>
<!-- End Facebook Pixel Code -->

The footer code is

<script
  src="https://code.jquery.com/jquery-3.5.1.min.js"
  integrity="sha256-9/aliU8dGd2tb6OSsuzixeV4y/faTqgFtohetphbbj0="
  crossorigin="anonymous"></script>

The custom CSS is 

.Header-nav-folder-item:first-child {
  display:none;}

#collection-595d6e3dff7c50d877d13701 {
  .image-caption-wrapper{
 padding-top:2px !important;}
}
 #header {
   width: 500px !important;
 }
 #logo.has-img {
   width: 450px !important;
 }
 .image-block { 
     width: !important; 
     padding-bottom: 7px !important; 
     padding-left: 7px !important;
     padding-right: 7px !important;
     padding-top: 7px !important;

}
.tweak-index-page-scroll-indicator-icon-arrow:not(.tweak-index-page-scroll-indicator-none) .Index-page-scroll-indicator-arrow {
display: none;
}

.sqs-gallery-controls .previous:hover, .sqs-gallery-controls .next:hover {
   background-color: #DD571C;
  opacity: 40%;
}
.sqs-gallery-block-slideshow .sqs-gallery-controls .next,
.sqs-gallery-block-slideshow .sqs-gallery-controls .previous {
  background: none; 
}
.sqs-gallery-block-slideshow .sqs-gallery-controls .next::before,
.sqs-gallery-block-slideshow .sqs-gallery-controls .previous::before {
  background: none;
  color: #FF4500;
  font-size: 2em; 
  font-weight: bold;
  padding: 0px;
  border-radius: 50%; 
}
.quote-block {
padding: 0px 0px 0px 30px !important;
}
.Header.Header--top {
  position: fixed;
  top: 0px;
  z-index:1000;
  width:100%;
  box-shadow: 0px 2px 3px rgba(0,0,0,0)
}
.Intro {padding-top:100px;}
.Index {padding-top:100px;}
.Main {padding-top:0px;}
.Main.Main--page {padding-top:100px !important;}
.Main.Main--blog-item {padding-top:150px !important;}
@media only screen and (max-width: 480px) {
  .Main {padding-top:0px !important;}
  .Intro {padding-top:100px !important;}
  .Index {padding-top:100px !important;}
}
.sqs-layout.sqs-editing .sqs-block, .sqs-block-spacer-content {
    min-height: 0px !important;
}
.sqs-block-spacer .sqs-block-content {
  height: 0;
}
.sqs-block-spacer {
    padding-top: 0 !important;
    padding-bottom: 0 !important;
}
.image-block:hover img {
filter: brightness(50%); 
  opacity: 1;
  transition: all .3s ease-in-out;
}
.collection-5961ad0a099c015c9e414da3 .image-block:hover img {
  filter: brightness(100%) !important;
  transition: none !important;
}
.collection-5ee7c6229cbc990dedfe9eb6 .image-block:hover img {
  filter: brightness(100%) !important;
  transition: none !important;
}