Echo JS 0.11.0

In fact, it's the .cbp-so-scroller (.portfolio) section that needs an overflow-x of hidden. 

The way I worked this out is by adding a border of 1px to everything. I saw that when .cbp-so-side-right animated in, it was using the space that was created as it is starting to fade in at that point, meaning it is visible on the DOM.