Grey Line Site Error

I've just gone live with my site and suddenly have an issue where the background photo displays incorrectly and there is a  grey bar appearing below the image, above the footer.

In the back end, the same issue appears, but on the home page instead of /about, and only when the page isn't fully expanded.

This isn't an error, you have a header at the top, a footer at the bottom which take up ~10% of the viewport (window) height, and on this page you have one section that takes up ~75% of the height, so the grey is simply the extra space that isn't header, footer, or page content.

To get rid of that, on a page with just one section, make sure the section height is set to L (large).

Hey @Ziggy thanks so much

That all makes sense.