rand not working

I am trying to show two random posts on the right hand column under the purple Hot Travel Deals banner. This is the shortcode I used:[display-posts orderby=”rand” posts_per_page=”2″ category_id=”88″ include_excerpt=”true” image_size=”large” wrapper=”div” wrapper_class=”display-posts-listing image-top”] but it is only showing the same two posts every time.

Any help would be great.

Sharon

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