Following the posting of an image of a crack in a link on a Petzl Zigzag Mechanical Prusik a few weeks back, Petzl have now had the Zigzag in question back and have completed their investigation.
Following comprehensive testing and auditing of their inventory of Petzl ZigZags, Petzl have concluded that a cracked link presents no additional risk to the user (however, the presence of such a crack requires immediate retirement of the ZIGZAG).
Their full statement can be found by clicking the image below: