Aha, I now realise that the whole messed is based on my use of select fields and not text fields with the wp_kses_post() function.
Many have had this issue to fight with it looks like.
http://support.advancedcustomfields.com/forums/topic/acf_form-security-documentation/
I will now try to use your function:
function acf_wp_kses_post($data) {
if (!is_array($data)) {
return wp_kses_post($data);
}
$return = array();
foreach ($data as $index => $value) {
$return[$index] = acf_wp_kses_post($value);
}
return $return;
}