Yes I did some work on the calc file, but in a local copy, independent local files.
Indeed we have a problem with the export of PDF with hidden section, the links result wrong and points to the wrong page. Also, the larger the file the worse. The bug affects the exported TOC and its bookmark export in the PDF, and perhaps more unseen troubles.
When editing the source file (a large odt file or a large master document - odm), LibreOffice links and references does work without any flaw (that I could have noticed). The issue is on the exported PDF with hidden section. There you'll see the TOC displays the correct page number but the link in the TOC is wrong.
The bug has been narrowed by Ilmari and is
On the 6.2 chapter files in tdfcloud, I noticed a small and invisible issue: the section hide condition in chap 10 ad 14 has a typo. Fixing in place (published folder).