Formatting error on Smashwords ebooks

A reader was kind enough to point out to me recently that the epub versions of RealmShift and MageSign had a formatting error. It seems that the font size switched between 10 point and 12 point fairly randomly throughout both books on some readers.

I checked this on my iPhone and found that on Stanza Desktop the books looked fine, but once uploaded to the iPhone Stanza they switched font sizes every few paragraphs.

So, having investigated, it turned out to be publisher error. In other words...