Riley Nix (Instagram, @riley.nix) sent me the videos below. (I’m sharing them with his permission.)
When he was top rope soloing, he was rather alarmed to discover that his Petzl Micro Traxion, installed correctly with the cam engaged, was definitely NOT grabbing on his slightly iced up rope. Yikes!
Would a similar backup device have worked in this situation? Who knows? If it's a toothed camming device like that, that might've failed too.
This is a good reminder to have a backup to your progress capture pulley if there's a slightest chance it could get jammed up with snow, ice, or if you're using it on an iced up rope.
For crevasse rescue, it's good practice to tie a hard backup (typically, a bight knot) for every few meters of rope you pull up.
Another crevasse rescue tip: excavate a small sort of bowl out of the snow underneath the pulley. This lets the pulley sort of hang in the air instead of being mashed into the snow and potentially having this problem.
Petzl Traxion pulley failing to properly engage on an icy rope. Video by Riley Nix.
Close up of Traxion pulley failing to properly engage on an icy rope. Video by Riley Nix.