My chapter is titled just "Chapter 1", and my export prints "Chapter 1" twice. How do I fix it?

From version 1.9.24, a chapter whose title is only its label, such as "Chapter 1", "Chapter One" or "Chapter I", prints it once, in the size of a chapter title, in the PDF and in Word alike. The fix is made when you export, so books imported or written before also print it once, with no change to your files: just export again. In an older version, delete the "Chapter 1" line at the top of the chapter's text in the editor, or give the chapter a title of its own.