Yanki had broken his hand twice, less than six months after his Bar Mitzvah. Once he fell off his bike, and the second time he slipped down a flight of stairs. He had his Mezuzos checked and all was okay. After breaking his left hand the second time, his father decided to check the Tefillin. The sofer checked the Tefilin but found nothing wrong. Just to be positively sure, he sent the Tefillin to the Vaad Mishmeres STaM for a computer check. Sure enough there was an incorrect letter in the text which the sofer had failed to pick up.