Please send to contact[at]phpdocx.com the DOCX and we'll check it. What version of LibreOffice are you using?
Also please note that embedHTML includes disableWrapValue and removeLineBreaks options to prevent adding blank spaces and line breaks when adding HTML. Some versions of PHP Tidy add break lines when doing the transformation from HTML to DOCX that MS Word ignores but LibreOffice shows. Please try to enable both options.