The MOBI6.init() method builds #fileposList (the map of all filepos byte-offset references, used to insert <a id="fileposXXXX"> anchors into section HTML) after calling getGuide() and the TOC-section loader — both of which call createDocument() → loadText(), which caches the section HTML. Since #fileposList is still empty at that point, the cached HTML has no anchor elements.
Later, when Foliate calls getElementById('filepos12345') on the cached (anchor-less) document, it returns null, so the paginator falls back to ?? 0 — i.e. scroll to position 0 = first page.
For EPUB this doesn't happen because chapters are separate files; navigation loads a new section by index, not by searching for an anchor element within one section.
Co-authored-by: Lars E. <lars@ermert.es>
