DO you by any chance have an ORIGINAL_EPUB format? If so -- that will be used as the source for any EPUB ==> MOBI conversions.
And
it hasn't been edited.
Delete it if it exists, then reconvert.
EDIT:
Warning!!! Uncontrollable massive offtopic ahead! You can ignore pretty much anything that follows, up until and including the point at which you add something actually useful to the conversation.
Sorry about that.