Sidebar Not Stacking Properly

Greetings. I am just learning how Drupal works, so I am by no means fluent with how things are laid out and structured, but becoming familiar as I try to fix the following issue:

The sidebar (to the right of the body) is staying a fixed width and the body collapses when the browser is resized, but does not stack underneath of the body when the

browser reaches a certain specified size (as it previously had). I’m hoping this is something I would be able to fix. The issue is happening with a content type called “Content with Sidebar.” I have looked between our previous archived version of the website through Pages, Panels, Blocks and Content Types but cannot find any inconsistencies.

I appreciate any insight one can provide.

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/22/feed