WP-JSON - Multi-endpoint - Re-occuring Foreach Error - php

Question

I'm currently trying to build out a multi-endpoint system for WP-JSON between 4 websites, and most of the time it's fine, however sometimes when my page performs the process, it will throw back an error for the Foreach cycle, saying 'Warning: Invalid argument supplied for foreach() in ...'
I've tried alternative methods of merging the arrays before retrieving the body using wp_remote_retrieve_body but there's no such luck. I've looked up various google solutions on multiple-endpoints using php but nothing i've found seems to do an effective job
<?php
function limit_text($text, $limit) {
if (str_word_count($text, 0) > $limit) {
$words = str_word_count($text, 2);
$pos = array_keys($words);
$text = substr($text, 0, $pos[$limit]) . '...';
}
return $text;
}
/* BASE DETAILS FOR SEARCH*/
$b_url = get_site_url(); // Base URL
$posts_merged;
$args = array(
'sslverify' => false
);
if($_GET['search'] or !empty($_GET['search'])){
$filter_query = '?search='.$_GET['search'];
}else{
$filter_query = '';
}
$post_url_collective = array(
$b_url.'/wp-json/wp/v2/posts'.$filter_query, // Main Site
$b_url.'/db/wp-json/wp/v2/posts'.$filter_query, // DB Site
$b_url.'/dc/wp-json/wp/v2/posts'.$filter_query, // DC Site
$b_url.'/fw/wp-json/wp/v2/posts'.$filter_query // FW Site
);
$post_response = wp_remote_get($post_url_collective[0], $args);
$post_response = wp_remote_retrieve_body($post_response);
$post_response = json_decode($post_response);
$post_response_two = wp_remote_get($post_url_collective[1], $args);
$post_response_two = wp_remote_retrieve_body($post_response_two);
$post_response_two = json_decode($post_response_two);
$post_response_three = wp_remote_get($post_url_collective[2], $args);
$post_response_three = wp_remote_retrieve_body($post_response_three);
$post_response_three = json_decode($post_response_three);
$post_response_four = wp_remote_get($post_url_collective[3], $args);
$post_response_four = wp_remote_retrieve_body($post_response_four);
$post_response_four = json_decode($post_response_four);
$posts_merged = array_merge( $post_response, $post_response_two, $post_response_three, $post_response_four );
?>
<div class="container multi-search-wrap">
<div class="row" style="margin-bottom: 0px">
<div class="col sm12 m12 l12">
<form class="multi-search-form" method="GET">
<div class="row" style="margin-bottom: 0px">
<div class="col sm8 m9 l10">
<input type="text" name="search" value="<?php echo ( isset( $_GET['search'] ) ? $_GET['search'] : '' ); ?>" placeholder="Search for..."/>
</div>
<div class="col sm4 m3 l2">
<input type="submit" value="Search" />
</div>
</div>
</form>
</div>
</div>
<div class="row" style="background: #eeeeee;padding: 10px;font-size: 12px;margin:0px 0px 20px 0px">
<div class="col sm12 m12 l12">
We've found <strong><?php echo count($posts_merged);?></strong> results for <?php echo $_GET['search'];?>...
</div>
</div>
<div class="row">
<?php
// Post Loop
foreach($posts_merged as $get_post) {
$image_url = $b_url.'/wp-json/wp/v2/media/'.$get_post->featured_media;
$image_response = wp_remote_get($image_url, $args);
$image_response = json_decode($image_response['body']);
//echo'<pre>';print_r($image_response);echo'</pre>';
echo '<div class="col sm12 m6 l6 multi-search-post">';
echo '<div class="row">';
echo '<div class="col sm12 m3 l4 multi-search-post">';
if(!empty($image_response->media_details->sizes->thumbnail->source_url)){
echo '<img class="img_'.$get_post->id.'" src="'.$image_response->media_details->sizes->thumbnail->source_url.'" width="auto"><br>';
}else{
echo '<img class="img_'.$get_post->id.'" src="'.get_template_directory_uri().'/images/post-placeholder.jpg" width="auto"><br>';
}
echo '</div>';
echo '<div class="col sm12 m9 l8 multi-search-post">';
echo '<a href="'.$get_post->link.'">';
echo '<h3>'.$get_post->title->rendered.'</h3>';
echo '</a>';
echo '<p>'.limit_text($get_post->excerpt->rendered, 30).'</p>';
echo '</div>';
echo '</div>';
echo '</div>';
}
?>
</div>
</div>
I would like to improve the load speed of the queries but the most important part is ridding this occassional Foreach error.
Any help would be greatly appreciated