looks like the euro cylinder is faulty if its a double glazed door. search google for euro cyclinder and you will see the pics. its best to remove and replace it. to do this open the door, where the key goes into the lock on the inside of the door is a screw reove this screw. then turn the key slowly round and you will find a point where the whole barrel slides out. now take it to the diy shop get the same 1 and replace it
kash, January 2013
