Structure-based assignment of section types not working in a project (solution enclosed)

I wrote out this post, then found the solution before I posted it. I’m posting it here in case someone else encounters the same problem.

In one of my projects, structure-based section type assignment is working just fine.

However, in my main project, it isn’t. No matter what type I assign to the various files and folders, everything is given the type “title page.” “Title page” shows up wherever I check it (outliner, inspector). It says “Structure-based from [name of root folder].” The root folder isn’t even assigned the type “Title page,” though. Nothing I change seems to make any of the section types change.

Is there any way I can reset this project somehow, so that it might work properly?

HOW I SOLVED THE PROBLEM: I erased the too-powerful section type (“Title page”) and everything was assigned its correct type. I then created a new “Title page” type without problems.

Could you have accidentally at some point selected the root folder and then selected “Title Page” from Section Type > Default Subdocument Type? That would make it so that all subdocuments of that folder have their structure-based section type overridden to “Title Page”. It sounds as though that happened somehow.

All the best,

Maybe. It would have been a strange accident, though, because I hadn’t really used styles before this.

I think I checked that, but at this point I can’t be sure.

I meant, of course, that I hadn’t used section types.