So this isn’t a full solution, but it at least allowed me to get the images from the custom image fields to display. Still seems to be a problem with YARPP but this seems to get by the problem at least for images.
I noticed like you said that the image field was returning the ID of the image even though in my case I have it set to return the image URL to be used as a background image.
I just fed that image ID into wp_get_attachement_url() and was able to use that url to display the image.
<?php $imageId = get_field('post_featured_image');
$imageUrl = wp_get_attachment_url($imageId); ?>
<a href="<?php the_permalink(); ?>">
<div class="relatedsingle" style="background-image: url('<?php echo $imageUrl; ?>');">
<div class="singleoverlaygreen"></div>
<h4><?php the_title(); ?></h4>
</div>
</a>
This is obviously only to get the image url for a simple application like mine, but my guess is that you could use wp_get_attachment_metadata() instead of wp_get_attachment_url() to fetch anything from the image array that you would otherwise gotten from the ACF field.
