Some of the books on Wikisource like this one has a Table of Content ordered alphabetically and not according to page numbers. See for example. As Wikisource Export tool depends on the TOC order, it arranges the exported pdf or epub file erroneously according to the alphabetical order.

Possible solution: If the Wikisource export tool take care of the |next= and |previous= parameter in the header template, the issue might get resolved.