This was a really tricky one and thanks to Patrick’s help from ACF we figured it out. It had nothing to do with the Post ID and the method of getting the ID but rather the fact that the select field had been checked for “Use AJAX to lazy load choices?” and apparently when this is active you can’t get the ID to use with load_field but rather have to hardcode it. So we turned it off and all is fine now.
Thanks again
