If you hear the crack, take it easy winding them off or on.. If you do hear the cracking noise, it'll be pattern in the head of the key giving way so a spare one at hand would be ideal! As I'm usure how long a replacement will take coming back to you.
When I contacted McGard, they said they would need the damaged one back before they would ship out a new one. But replacements are 18euro, just send them your 17 digit key number and they will get one out to you right away.
