I carry two extended cuff keys when working. My primary has always been a Zak Tool key on an enlarged split ring carried on a belt keeper. I keep a standard pen style key with a clip tucked into my uniform shirt in the space between the buttons. I just tried using the one on my keeper to unlock a set of cuffs and it didnt work. It goes into the key hole, but wont turn at all in either direction. It has never failed before. I used my pen key and it worked perfectly. The trouble key is at least 10 years old and has been used a lot. I dont mind replacing it with a new one, but I was just curious if this has ever happened to anybody here? Does the metal get bent out of spec ever so slightly over time? I dont see any hairline cracks in it anywhere.