network_get_comments_number updates only on sub blogs

The website is Try posting some comments: the first blog post from top is on sub-blog "" and as soon as you hit the "post comment" button the main page updates with post comment. But when you post comment on any of main page posts, the comment count stays at zero. I don't know how I managed to update it for one of posts, but I cannot replicate.

Any help is greatly appreciated.