Hi @mcseay
CPT-onomies has a weird structure as it forces a post as a taxonomy. To get the custom field, you need to pass the id of this post (the post that is converted to a taxonomy) as the second parameter. Something like this:
<?php $image = get_field('headshot', $cptonomies_post_id); ?>
where $cptonomies_post_id is the id of the post.
I hope this makes sense.