Too much space on right hand side of page

Site URL: https://celery-prism-5xaj.squarespace.com/

I am working on my portfolio style home page.

https://celery-prism-5xaj.squarespace.com/

Password is FF2205

Looking at it the blocks are nicely placed in the centre of the page. However, there seems to be loads of padding/ margin/ space on the right hand side of the blocks. On my MBP when I double finger drag across the page, I can push the content off the left hand side of the screen. 

Why is my page so wide?

I don't want to be able to horizontally scroll the page. 

In Design>Site Styles>Spacing I have the Site Width (Max) set to 1920, Site Margin 2vw.

On other pages that don't have the same design I am not having this issue.

Any thoughts?

Thanks

Update:

The problem seems to be caused by code blocks that include iframes.

When I remove them the page behaves correctly. Am I missing some code in the iframe html?

This is an example of how one of my blocks is coded.

<div style="padding:56.25% 0 0 0;position:relative;">
  <a href="/tvc/angela-scanlon-for-olay/" style="position:absolute; top:0; left:0; display:inline-block; width:1000px; height:500px; z-index:5;"></a>
  <iframe src="https://player.vimeo.com/video/710075469?background=1?autoplay=1&loop=1&title=0&byline=0&portrait=0" style="position:absolute;top:0;left:0;width:100%;height:100%;" frameborder="0" allow="autoplay; fullscreen" allowfullscreen>
  </iframe>
  </div>
<div class="overlay">
    <h2>Marc Jacobs Beauty</h2>
  <h3>WINONA RYDER</h3>
  </div>
 

I can't see what would cause the problem. Any thoughts?

Try adding to Design > Custom CSS

html, body {
    overflow-x: hidden;
}