plugins folder not included in backup

Hi
I've setup snapshot pro to make a daily backup of the database and all the files (plugins, themes and files) - I've included a screenshot of the configuration.
I checked the first backup and everything is inside, except for the plugins folder.

I have to say I renamed the wp-content and plugins folder by setting the WP_PLUGIN_DIR & WP_PLUGIN_URL constants in wp-config, I use this setup:

define('NR_SITE_URL', 'http://example.com]);
define('WP_CONTENT_FOLDERNAME', 'assets');
define('WP_CONTENT_DIR', ABSPATH . WP_CONTENT_FOLDERNAME );
define('WP_CONTENT_URL', NR_SITE_URL.'/'.WP_CONTENT_FOLDERNAME);
define('WP_PLUGIN_DIR', WP_CONTENT_DIR . '/extra' );
define('WP_PLUGIN_URL', WP_CONTENT_URL.'/extra');

This means I have a folder "assets" in my root (instead of wp-content), inside this folder is the plugins-folder, which has the name "extra".

I think Snapshot Pro assumes the plugins folder always has the name plugins.. ?