I sent one again this morning to my Kindle using Calibre and I didn't even have to convert it first, I loaded the RTF into Calibre, connected my Kindle, and clicked Send to Device, Calibre asked me if I wanted to convert it first, I said yes and Calibre created a MOBI file. I checked the book on my Kindle and the formatting looks perfect to me. Title and Author correct, and even the picture at the front of the book is perfect.
I hope this helps. I am not technical so don't understand code (although I know what it is as I test computer systems from a user perspective for a living)