When I'm creating Default Sets of Fields and I click save, I get an error 404. This will happen when wp is installed in a sub-directory.
This fixed the issue for me. Please check with creator of plugin if this s ok.
Edit the following file on line 287. (If not there search for the __construct function).
buddypress-group-extras > core > admin.php .
Go to line 287.
remove the site_url and replace it with home_url.
It should look like this thereafter.
wp_redirect(str_replace('&saved', '', home_url($_POST['_wp_http_referer'])).'&saved');