Page editor goes 404 when updating.

I have setup my site with this theme and I am working on adding some content to it now.

I have created a page, which I wish to place 4 images on that will work like a menu.
But when I use the page editor that is included in this theme and I attempt to add a “Single Image” section with that image being a link as well to another page.. It just 404’s when I attempt to update the page.

I can use seemingly any other element, but when I attempt to add an image to the page and I save the page, it crashes.

How do I fix this?