[Oldpilot]

Epubcheck doesn't like my endnotes! Here is a typical note as rendered in Sigil, having first been converted from mobi to epub format by Calibre):

<p class="calibre4"><a class="calibre9" href="../Text/visionepub_split_012.html#filepos91308" id="filepos181022"><span xml:lang="EN-GB">[103]</span></a> Ibid.</p>

And here is Epubcheck's complaint about it:

ERROR: visionnook.epub/OEBPS/Text/visionepub_split_018.html(631): 'filepos91308': fragment identifier is not defined in 'OEBPS/Text/visionepub_split_012.html'

The notes work just fine in Sigil Book View. That is, if I click on the 103 in the citation, it takes me back to the correct place in the text, and again if I click on the 103 in the text, it takes me to the relevant citation.

Some forty-odd endnotes follow this one, about which Epubcheck has nothing bad to say. Indeed most of the complaints are about the notes in a single chapter.

Where should I begin to look for the underlying error?

(I have uploaded the epub to Barnes & Noble as it stands, and the Preview was perfectly in order.)

Thanks!