Some topics in TOC not showing in output

Hi, Everyone.

When I generate output of my TOC, the first 2 tiles reflect the TOC. But then Tile 3 skips ahead in the TOC by 12 topics (and 2 books), to Topic 15.  

This TOC seems completely messed up in other ways, too. Most strange of all is that, I initially deleted topics 3 - 15 in an unrelated effort to find a "bad" topic that was preventing me from generating output. After finding the offending topic, I wanted to go back to reintroduce the topics I deleted. Those deleted topics each had a red "x" next to it. I intended to reintroduce each topic that had a red X. But after reintroducing the first of these and pressing ctrl + S,  all the red x's disappeared.

Okay...  Those topic titles remained in the TOC, but now with no red X. (See screenshot.)

Maybe their presence is just an empty "shell"; maybe they're not really "there." I generate the output, and, sure enough, the output does not display those topics. Fine. 

However, I reintroduce several of the actual topics to the TOC and delete the corresponding "shells." And the output still skips over the newly replaced topics.

Thank you.