Well ... here's what I was doing.
'Single File.epub' has 4 H1's with the links to the first 3 in the fourth. Works just as I'd expect. Everything in Section0001 (because there is only one)
Created an anchor in the first 3 H1's and links in the fourth (below):
Code:
<h1 id="sigil_toc_id_22">Here there be links</h1>
<div>
This is <a href="#Link_One">link one</a>
</div>
<div>
This is <a href="#Link_Two">link two</a>
</div>
<div>
and this is <a href="#Link_Three">link 3</a>
</div>
Then I split each H1 into a seperate chapter/file (Chapter Split.epub)
so this used to be in Section0001 with its anchor also in Section001.
Code:
<a href="#Link_One">link one</a>
However, now the above href is in Section0004 and its anchor is still in Section0001
Similarly for the other two href's -- their anchors are in Section002 and Section003
HTH
Paul