Hello,
What version and license of phpdocx are you using?
There's no known bug when working with custom styles and the pStyle option is fully tested and working. Maybe the correct style name is not being applied. We'd need to check the code you are running to know what method you are using and some DOCX file with that style that is not being applied correctly. If you are using an old version of phpdocx please check the documentation available on https://www.phpdocx.com/news/post/important-changes-for-lists-in-the-last-ms-word-update/221.
Regards.