I’m assuming you are doing this within the loop and you don’t have to set up postdata. With that said, since you have a post object field inside a repeater, you dont have to use the foreach loop.
<?php while(has_sub_field('post_links')): ?>
<?php $post_objects = get_sub_field('items'); ?>
<ul>
<li>
<a href="<?php echo get_permalink($post_objects->ID); ?>"><?php echo get_the_title($post_objects->ID); ?></a>
</li>
</ul>
<?php endwhile; ?>
