For my ebooks, I define my chapter headings in Word (on a Mac) as "Heading 1".
When I input the docx file into Calibre (epub output), it creates a Table of Contents with those chapter names. And when I do a page forward in Calibre's e-reader, when I'm at the end of a chapter it jumps to a new page for the start of the next chapter.
And they're not all chapter names. For example, the very first "Heading 1" is the name of the novel for the cover page (where I have the title, copyright info, etc) before Chapter 1.
I just formatted a new 11-chapter novella. I decided to have a preview section at the end with a preview page and some preview chapters of another novel. I have a "Heading 1" PREVIEW at the top of the preview page after Chapter 11 (the last chapter of the novella) and then I use "Heading 1" for "Preview-Chapter 1", "Preview-Chapter-2", etc.
The Table of Contents looks fine. But at the end of Chapter 11 (the last chapter of the novella), it doesn't go to a new page for the PREVIEW page. And both Chapter 11 and PREVIEW in the Table of Contents are bolded.
The way I got around it was to put in a manual page break before the PREVIEW heading.
Any idea why I had to do that?