My guess is that the loop in your function is interfering is some way with the global $post value. This can be caused by many things. I actually just had a similar problem on a site myself and it took me a long time to track it down.
My suggestion, to rule this out, would be to not use have_posts() and the_post() at all and instead to access the post information a different way.
if (count($sectors->posts)) {
foreach ($sectors->posts as $post) {
// vars
$value = $post->ID;
$label = ucfirst(str_replace('Fabrication for ', '', $post->post_title));
// append to choices
$field['choices'][ $value ] = $label;
}
}
you should not use wp_reset_postdata() if you use the above code
