I’ve created a support ticket:
I have a annoying issue / bug with missing fields in the exported JSON file and generated PHP file. So it’s not possible for me to …
1. … export my existing field group and import it again to a other wordpress installation.
2. … use “include_once( get_template_directory() . ‘/inc/acf-field-groups.php’ );” to load the field groups from the generated PHP file instead of the JSON file for user which are working with a child theme.