wordpress - WP_Query sometimes returns zero results when there are matching posts - why? -

this 1 has got me stumped.

i have category.php file contains loop:

<?php if ( have_posts() ) : ?>     <?php     while ( have_posts() ) : the_post(); ?>         <div class="entry-content description clearfix">             <h2 class="category-subtitle"><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>             <?php echo the_content(); ?>             <?php global $withcomments; $withcomments = 1;     ?>         </div><!-- .entry-content -->     <?php     endwhile; else :     get_template_part( 'content', 'none' ); endif; ?> 

this block of code works fine , returns results 1 expect.

in addition, outside loop (after it, in case matters), i've got column 1 side loop - i'm going refer newsfeed loop sake of clarity:

<h3 class="newsfeed-heading"><a href="/category/news/">latest news</a></h3> <?php     // wp_reset_query(); * same results or without wp_reset_query     $args = array(     'cat' => 89,     'order'   => 'asc'     );     $custom_query = new wp_query($args);     //echo "<h2>found: $custom_query->found_posts</h2>";     while($custom_query->have_posts()) : $custom_query->the_post(); ?>     <div <?php post_class(); ?> id="post-<?php the_id(); ?>">         <h4 class="highlight1"><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h4>         <p><?php $content = get_the_content(); echo mb_strimwidth($content, 0, 160, '...');?></p><div class="morelink"><a title="<?php the_title(); ?>" href="<?php the_permalink(); ?>">read more</a></div>     </div> <?php endwhile;    // wp_reset_postdata();  * same results or without wp_reset_postdata ?> 

now, in majority of cases, these 2 loops play nicely , both loops return set of results i'd expect. not always.

as far can tell, think if main category loop contains 1 result, newsfeed loop correct. if main category loop has multiple posts in results set, newsfeed loop works fine. have not been able spot pattern.

i have tried putting wp_reset_query(); in different places, clutching @ straws, doesn't make difference.

incidentally, when newsfeed loop works, returns correct results set. when doesn't, returns nothing , $custom_query->found_posts returns zero.

i appreciate advice on possible solution.

you missing wp_reset_postdata(); after custom query. call the_post(), setting $post global value of current post. true main query , custom instance of wp_query. in get_posts, happens when call setup_postdata().

as pointed out, wp_reset_query() used query_posts should never use breaks main query object , relies on main query object related posts, pagination , page functionality.

if above not work, posts_** filters or instance of pre_get_posts poorly written in theme or plugin. apart these suggestions, code should work.