This year I've been using Calibre as a conversion engine to take in a word file and put out epub. I then use Sigil to tweak. Recently I've noticed some justified paragraphs that mid-way through become left aligned, then sometimes even switching back to justifed. So the middle of a paragraph, for example, might be left aligned.
When I look at the code I see something like this:
<p>It is fairly apparent that high performing organizations have favorable <span class="calibre4">cultural profiles. </span> In addition . . .
Where calibre4 is defined as white space: pre-wrap; and pre-wrap messes up justification.
The odd thing is that there is nothing in the word document to occasion any special treatment of those two words. They are just in the middle of a paragraph.
One of my documents has hundreds of these seemingly random spans. I redefined the class as white space: normal; and everything went back to proper justification. Any idea what might be going on? Anyway, if you do conversion with Calibre, keep an eye on paragraph justification.