Doitsu, I am a he
Yes, I im learning how to create ePub3 validated books because in my opinion and others that I work with is the way to go. It might not be working properly now on certain eBooks readers but eventually I believe they will pick up the pace and conform to the standard.
Since I checked the new version of Calibre I can do pretty much what ever I need to edit epubs and it is convenient for me as Sigil, that being said, Sigil is not being maintained any longer so what's the point in trying to fix bugs?
In addition, it is probably my files only because when I checked the epub samles on:
https://code.google.com/p/epub-samples/downloads/list
I never got an error so it must have something to do with the conversion process when I used Calibre.
Thanks anyway.