Link to random post messes up navigation

I am using a navigation to go from post to post:

<?php next_post('%', '<img src="http://www..." alt="previous"> ', 'no'); ?>
<?php previous_post('%', '<img src="http://www...." alt="next"> ', 'no'); ?>

and I want to have a “random post button”:

<?php $posts = get_posts('orderby=rand&numberposts=1');
foreach($posts as $post) { ?>
<a href="<?php the_permalink(); ?>" >RANDOM</a>
<?php } ?>

This works fine – but when I place the random button between the previous and the next button, then it messes up the next button (which becomes random too).

Any ideas how I could fix that?