comments_template() doesn’t work with ajax call

I partially resolved adding this code:

$args = json_decode( stripslashes( $_POST['query_vars'] ), true );     
$args['paged'] = $_POST['page'];    

//Set Query Post args
query_posts( $args );

//Set Glboal Post Data
global $post;
$post = get_post( $_POST['post_id'] );
setup_postdata( $post );

//Set global $withcomment = true to execute comments_template() - using comments-ajax.php Template (Root Folder Theme)
global $withcomments;
$withcomments = true; 
comments_template('/comments-ajax.php');

and this in my js:

post_id: ajaxfrontendobject_get_comments.post_id,

Now it works but if I click on the page number (using ajax request) on which the site initially loaded (without using ajax) no comment is loaded and I don’t understand why.