Hello,
phpdocx 10 is fully compatible with the API of previous versions (the API is the same but adding new options, classes and methods). It doesn't have changed anything related to how MS Word styles are handled; maybe you need to enable some option?
phpdocx doesn't remove contents or styles from a template unless specific methods are used.
Please send to contact[at]phpdocx.com the most simple script (and the template) that illustrates your issue, the version number you were using before phpdocx 10 and both DOCX outputs (using phpdocx 10 and the other phpdocx version).
Regards.