Hello,
We recommend you to check you are settings widths to tables and cells when creating them (https://www.phpdocx.com/documentation/conversion-plugin/preparing-the-templates-for-its-conversion):
Set the sizes of the tables manually when using addTable or embedHTML methods. So, instead of keeping the sizes with automatic values according to the content, indicate specific values for each row, column and cell.
Also please check you are using the latest release of LibreOffice (www.libreoffice.org).
Regards.