Website has a small horizontal offset, especially on mobile devices

Hi! My client reported a small horizontal offset on their website, with a horizontal scroll bar appearing on the bottom of their browser. I can't figure it out, been looking with developer tools and CSS but haven't found a solution. There seems to be no overlap, yet it allows the browser to scroll right a tiny bit outside the contains of the website. It only seems to appear on the home page.

I've disabled the caching plugin.

Cheers,
Alex