After googling for some solutions or alternative plugins, I came across this fix for the Excerpts field from the plugin's author: https://gist.github.com/mgburns/8423646
This fix makes the Yoast SEO fields and the Excerpt field editable on a cloned page. Just create the PHP file (from the github link above) in the BU Versions plugins folder and upload it to your server. Then activate it in the WP backend (yourdomainhere.com/wp-admin/plugins.php).
I hope this helps someone who needed the extra functionality on an already nice plugin. If we could also clone the custom fields, this plugin would be perfect!