someone give me a solution:
at wp-includes\post.php line 1289:
$post_name_check = $wpdb->get_var($wpdb->prepare("SELECT post_name FROM $wpdb->posts WHERE post_name = '$alt_post_name' AND post_type = '$post_type' AND ID != %d AND post_parent = %d LIMIT 1", $post_ID, $post_parent));
change to
$post_name_check = $wpdb->get_var("SELECT post_name FROM $wpdb->posts WHERE post_name = '$alt_post_name' AND post_type = '$post_type' AND ID != $post_ID AND post_parent = $post_parent LIMIT 1");
But I don’t know why this works.