ACF Gallery Field: Pull from default language's images

functions.php

<?php

add_filter('acf/load_value/type=gallery', 'acf_load_translated_attachment_ids');
function acf_load_translated_attachment_ids($value) {
    // if the current language is the default language, 
    // then we don't need to fetch the translated ids
    if (acf_get_setting('default_language') == acf_get_setting('current_language')) {
        return $value;
    }

    // map throught each 'default language' id, and return the translated one
    return array_map(function($id) {
        return apply_filters('wpml_object_id', $id, 'attachment');
    }, $value);
}