Hi Stefan
Thanks for your reply. I have a LOT of section breaks in the document - so before and after each TOC page.
The challenge is that the actual page number is okay - it's the chapter number that's wrong. I've been able to upload some screenshots today so maybe this will show it better.
First up is a split screen that shows the section 1 TOC page and the first page of the section 1 content. The information in both headers is correct.

This section screenshot shows the same pages as above but I've pressed Alt+F9 so you can see the field codes.

This screenshot shows a split screen with the section 2 TOC header (with a section break before) and the first section 2 content header (with a section break between them).
The yellow highlighted fields are incorrect.
This time the TOC header is using the Section 1 Heading 1 and chapter in the page number. (It should be page 2-1). Note that the TOC is correct because I set up a bookmark for the entire section 2.

And the lucky last - the same 2 screens, but again I've pressed Alt+F9 so you can see the fields.

I hope that explains the issue. Both TOC headers are set up the same and both content headers are set up the same, but section 1 details are correct. Section 2 details are incorrect.