If your form provides repeatable fields, add this in your functions.php
https://github.com/Hube2/acf-filters-and-functions/blob/master/acf-form-kses.php
and replace default filter from:
add_filter('acf/update_value', 'wp_kses_post', 10, 1);
to:
add_filter('acf/update_value', 'acf_wp_kses_post', 10, 1);
