That is because ACF is trying to load the scripts that should only be loaded on the front end in the admin. The WP init hook fires on both the front end and admin. If you want to do this with a hook then you need to make sure you’re not loading an admin page.
add_action('init', 'brandpage_form_head');
function brandpage_form_head() {
if (!is_admin()) {
acf_form_head();
}
}
I’m not 100% sure it will work though. init is an extremely early hook. Have you tested it on forms on the front end?
