I've read about this problem on the rimfirecentral.com forums.
I can't remember what causes it, but he needs to send that P22 in to be fixed.
Unforunately, after about 1800 rounds with relatively few problems (failures), my P22 is starting to exhibit that "walking" safety problem, where the safety engages, or partially engages itself after a fired round! Looks like mine might have to go back as well!
Maybe this is a stupid question, but is your friend chambering a round first? Pulling the trigger without a round in the chamber will not do it. As I understand, for true double action, you have to chamber a round, decock the hammer, and then you are ready.