Since upgrading to PHP 7, we get the following error message related to your plugin on our shop pages. (I have replaced some info with XXXXX for privacy reasons.)
Warning: DOMDocument::loadHTML(): Tag figure invalid in Entity, line: 1 in /home6/XXXXX/public_html/XXXXX/wp-content/plugins/printfriendly/pf.php on line 256
Deactivating your plugin removes the error message.