[j.p.s]

Originally Posted by tomsem

Thanks, I do not have any encoding issues to deal with, but good to know.

I doubt there's anything wrong with the ePub in question but just want to try something else.

[update - And once again, STK has rejected it]

Do epubcheck or kindlegen have any complaints?

Neither necessarily maps directly to whatever STK doesn't like, but they might provide clues.