maybe_unserialize post metas on duplication

Serialized post metas (array or object) should be unserialized before duplication. Otherwise data will be serialized again.
See https://github.com/WordPress/WordPress/blob/master/wp-includes/functions.php#L610

My suggestion:

wp-content/plugins/bogo/includes/post.php line 319
… to have the original data before bogo_duplicate_post filter.

foreach ( $post_metas as $meta_key => $values ) {
    foreach ( $values as $key => $value ) {
        $post_metas[$meta_key][$key] = maybe_unserialize( $value );
    }
}