Hi there, when I unpack this file (attached below), it inserts random sentences/words in places, but it doesn't in calibre (I don't know if they use different algorithms).
Anyway, here is the file is in the attachments (pg71.mobi = On the duty of civil disobedience); it's from project guttenburg, although I expect that is of little help since, as I stated above, it can be read perfectly with calibre.
Any help appreciated.
(Edit: here's the output)