Need help with CMS Flexible Layout

I am currently working on this “Work” page for a portfolio that pulls from a CMS. Some of the projects open up into a lightbox if they only have a single video in the project and some open up into a full page if there is text and multiple videos in a project. For some reason, when viewing the site normally outside of the designer, there is a weird gap but I don’t ever see the gap in the designer. Screenshot below. But the gap only appears at certain viewport widths and whenever I change the browser zoom it goes away. Can someone take a look let me know what to change to get rid of the gap and keep the projects flowing normally?

Site link:

Here is my site Read-Only: