To clean up some Nook ePubs for loading on my Kobo Glo I'm doing these conversions:
* ePub to Mobi (which removes some formatting that the Kobo doesn't like)
* Mobi to ePub (which puts it back into ePub format)
Yesterday when I did this, I ended up with three files: EPUB, ORIGINAL_EPUB, MOBI
But today, doing the same thing only results in EPUB and MOBI.
I didn't touch the Tweak settings, and I've confirmed that I've got this setting: "save_original_format = True"
The conversion IS happening; the EPUB file in the folder for this book has a later timestamp than the MOBI file, but the original is gone.
I'm using Calibre 0.9.9 on Windows XP.