woocommerce ajax call using a template part - ajax

Question

I have set up a filter for products using ajax. It works fine when using a string as response but not when using a template part.
See below the part of the query
$qry = new WP_Query($args);
$responses = '';
if ($qry->have_posts()) :
while ($qry->have_posts()) : $qry->the_post();
$responses .= wc_get_template_part( 'content', 'product' );
//$responses .= '<h2 class="entry-title">'.get_the_title().'</h2>';
endwhile;
$response = [
'status'=> 200,
'found' => $qry->found_posts
];
else :
$response = [
'status' => 201,
'message' => 'No posts found'
];
endif;
$response['content'] = $responses;
die(json_encode($response));
and below is the ajax call
function get_posts($params) {
$container = $('#container-async');
//$content = $container.find('.content');
$content = jQuery('.products');
$status = $container.find('.status');
$products = $('.products');
$status.text('Loading posts ...');
$.ajax({
url: ajaxurl.ajax_url,
data: {
action: 'do_filter_posts',
nonce: ajaxurl.nonce,
params: $params
},
type: 'post',
dataType: 'json',
success: function(data, textStatus, XMLHttpRequest) {
if (data.status === 200) {
$content.html(data.content);
console.log(data.content);
}
else if (data.status === 201) {
$content.html(data.message);
}
else {
$status.html(data.message);
}
},
error: function(MLHttpRequest, textStatus, errorThrown) {
$status.html(textStatus);
console.log(MLHttpRequest);
console.log(textStatus);
console.log(errorThrown);
},
complete: function(data, textStatus) {
msg = textStatus;
if (textStatus === 'success') {
msg = data.responseJSON.found;
console.log(data);
}
$status.text('Posts found: ' + msg);
console.log(data);
console.log(textStatus);
}
});
}
In the inspect mode is see the following feedback
SyntaxError: Unexpected token '<', "<li class="... is not valid JSON
Am I calling the template wrong? or do i need to do anything else first?
The ajax function is working when using the return string $responses .= '<h2 class="entry-title">'.get_the_title().'</h2>';
How do I make it work when using the template part?
Thanks in advance!