@Kaetrin,
It sounds to me as if you are using calibre's default setting for page splits and that this particular book is totally unsuited for that default. Try the following:
Make sure you're converting from the original source azw3 and on calibre's
Convert - Structure Detection page try the following 2 settings:
Detect chapters at: /
Insert page breaks before: /
and on the
Convert - Table of Contents page, make sure the Level 1, Level 2, Level 3 TOC boxes are all blank
The calibre defaults were probably created for the early ebook days when it was necessary to split a solid wall of text into sensible chapter chunks. These days a well-designed retail quality ebook
should (but don't bet real money on it
) already be split into the correct chunks with a matching TOC so you don't need calibre to try and guess where the chapters start/end.
ETA: Also make sure that on the
Convert - Heuristic Processing page the 'Enable heuristic processing' is UNCHECKED