For conversions from epub or html --> mobi, Calibre is not recognizing the pointer to the TOC in the Guide section of the OPF.
When I make a reference using an Anchor, the reference fails.
<guide>
<reference href="filename.html
#toc" title="Table of Contents" type="toc"/>
But if I make a reference without pointing to an Anchor, then it works.
<reference href="filename.html" title="Table of Contents" type="toc"/>
I've used anchors of the following types;
<a id="toc">, or <a name="toc"> or both.
The failure manifestation is that the Table of Contents menu option in either Mobipocket Reader or the Kindle will not go to the referenced location.
The "Do not add Table of Contents to book" box is unchecked, and the "Force use of auto-generated Table of Contents" box is unchecked.
Note that anchor references work for the Copyright entry in the Guide section.
I'm using ver 0.8.17.