Pagination for custom query throws 404 errors on last pages

I'm using a custom query to get all CPT posts for the author in author.php. I have a lot of authors and a lot of content so I'm using the wp pagenavi plugin to paginate between these posts.

For some reason the pagination is giving me 404 errors on a lot of these pages. The pages that throw 404s is always the last or the two last pages of the pagination.

So for example /author/steve/page/8/ will work, while /author/steve/page/9/ and /author/steve/page/10/ will not.

I believe the pagenavi plugin handles 'paged' => $paged, but i've also tried setting $paged in the file: $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;, but with no difference.

Below is my query:

<?php
$author_id = get_the_author_meta( 'ID' );

if ( have_posts() ) : 

the_post();
rewind_posts();

$author_details = $wp_query->get_queried_object();
$curauth = (isset($_GET['author_name'])) ? get_user_by('slug', $author_name) : get_userdata(intval($author));
$temp = $wp_query;
$wp_query = null;
$wp_query = new WP_Query();
$wp_query->query(array(
  'post_type'=> 'publikasjoner',
  'paged' => $paged,
  'posts_per_page' => 4,
  'meta_key' => 'rapportnummer',
  'orderby' => 'meta_value_num',
  'order' => 'DSC',
  'author_name' => $curauth->user_nicename
));

while ($wp_query->have_posts()) : $wp_query->the_post(); ?>

// Post content

<?php endwhile; endif;

if(function_exists('wp_pagenavi')) { wp_pagenavi( array( 'query' => $wp_query ) ); }

$wp_query = null; $wp_query = $temp; ?>