Overflow hidden problem


On this site I have a homepage that has a neat scrolling animation as you scroll down the page. The picture of the van and also the boxes spread left and right respectively and disappear off the screen. All good.

Problem arises on the CMS collection ‘man and vans’ (accessible via areas covered - in the footer) which uses exactly the same css classes and IX2 transitions. For some reason on these landing pages the ‘overflow hidden’ on the parent element (section. header-section) is not being adhered to and you can see a big gap to the right of the page as you scroll down (as it ‘makes room’ for the boxes)

Any reason why it works perfectly on the homepage but not on the landing pages?

Here is my site Read-Only: LINK
Live site: https://www.u-movegroup.co.uk/

System info: 5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36