Hi there,
I don’t see a link to a screen shot in your post. To share a screen shot, upload the image to your media library, and paste the image URL here, or else you can use an image sharing service like snag.gy
Are you speaking of the line that can be seen either side of the page in the theme demo at https://isolademo.wordpress.com/? That is not random, but is a border this theme applies to the content area. If you don’t want that border to appear, you can hide it by adding this code in the Additional CSS section in the Customizer.
/* Remove vertical borders around site content area */
.site-content {
border: none;
}
If that’s not what you’re speaking of, please provide the screen shot. However, if it’s not something that’s visible on the theme demo page, it might be specific to your site. In that case I’ll need to know your site’s URL so I can check what’s causing it in the source code for your site.