ToC in pages document fails to display properly in sidebar

I have created a document of around 80 A5 pages.

All the way through, I have been using and checking the Table of Contents. Works absolutely fine.

When I export to PDF, and it is a PDF I want to distribute so this is important, the sidebar (e.g. in Preview but also in Adobe reader and browsers) fails to show the ToC. I just get the document name - but even that is truncated.

Thumbnails work fine - and I really don't care about them very much.

The ToC within the document works fine.

Using Sonoma 14.1.1 on M1 MacBook Pro and Mac mini.

If I export to Word, then export from Word to PDF, there are formatting issues, but the PDF ToC works fine!

Irony is that I recently switched from Word (which I've used for 30 years) to pages largely because of PDF creation issues in Word!