One page not displaying Sidebar

I am using Custom Sidebars throughout a site and they are all working except for one page. I have a Custom Post Type set up to be Hierarchical (ie. it has parent pages and child pages). A different custom sidebar is set up for each parent page and its child pages.

The one page that I am having trouble with is the very first page (both alphabetically and by ID) in this post type. It is the first parent page. It is defaulting to full-width-content as it apparently does not see that it has a sidebar selected.

• The theme default is right sidebar (content-sidebar).
• I am using the sidebar metabox on each parent page. I learned that it is not required to select a sidebar on the child pages. This works.
• On the page in question I have the correct Custom Sidebar selected.
• I also tried editing Sidebar Locations in the Widget.This shouldn’t be needed as it is specified on the page, but that didn’t work either.
• I cloned the page and still had the same problem

What I finally did was add a new page and copy the content from the old page – the sidebar worked! So, I change the parent of the relevant child pages, renamed the the old parent page (and saved as a draft for future reference), then renamed the new page to the old one.

Everything is working now, but I can’t figure out why that old page would not display the sidebar. I don’t know if the fact that is was a CPT is relevant, as the sidebars on all the other CPT pages worked. I don’t know if you will have an answer, but, if this does happen to someone else on just one page, try creating a new page, there was obviously some type of problem with the old page.