Woocommerce interfax issue

This is a weird issue. I have to take over a woocommerce (2.3.11) project. However, i am not a php programmer, neither am i familiar with wordpress and woocommerce framework. The project/website has an issue that hasnt been resolved by months. The issue is they use a plugin called checkout manager to add custom fields to the checkout page, and another plugin called woocommerce interfax to send fax when order is completed; However, each time the completion email includes all the extra custom fields created by checkout manager plugin, but the fax doesnt include any of those. Supposedly, the fax should use the exactly the same template as the email. Do you have an idea why? Any help will be highly appreciated Thanks.