User of these crews should inspect their kit as there have been a number of instances in which the screws have split along the length of the screw due to cold temperatures and the expansion differentials caused by a tight manufacturing tolerance.
Here is a post from an italian facebook group I'm part of from someone who says he's from Petzl:
"I’m Petzl’s Community Manager.
We have already seen this sort of crack. These cracks were due to a manufacturing tolerance between the tube and the teeth.
We have modified the manufacturing parameters and improved the mounting of the teeth in the tube.
The safety of the end user is not concerned as the resistance of the product remains within standard requirements (EN568).
However, the screwing performance may be affected.
We thank you very much for your feed back and ask you to return your product to your local distributor for replacement under warranty and analysis.
We're sorry for any inconvenience and stay at your disposal for any further information.
All the best
Baptiste - Community Manager - Petzl"
Here's a link to the facebook post complete with pictures:
https://www.facebook.com/groups/489385181118747/permalink/1295843177139606/