Post Slug randomly broke

I administer at site at http://www.farmcurious.com, and developed a custom theme for them.

The client noticed today that one of her URLs was broken. Sure enough, one of the products was only rendering a single image to the page, rather than all the of the content and text.

The post has been around for awhile, and on a hunch of changed the post slug from “jar-toppers” to “jar-topper” and that seemed to fix the issue.

Compare:
http://www.farmcurious.com/jar-toppers/
to:
http://www.farmcurious.com/jar-topper/

There are no errors of any kind that I can find. This only affect this one post, and no changes have been made to it recently.

Does anyone know what might have caused this?

Thanks in advance,
Jiert