The most familiar causes of a complete lock mechanism failure are doors which have dropped or doors which have twisted in some way. This is can be caused by a few things but the most ordinary reason for a door to twist is the weather, pvc doors move around all over in hot weather and then contract in cold weather. The most ordinary cause of a door to drop is age and weight. When your door has moved around this will usually throw all or some of the locking points out of line with the frame when you close the door, so as you try to lift the door handle, which you are necessary to do on 99% of composite and pvc doors it is very difficult to lift and as a result you are necessary to use a lot more force to lift the handle far enough to allow you to turn the key. Because the locking points catch on the frame as you force the handle up it puts a huge amount of pressure on one of the weakest parts of the multi point method called the follower. Locksmith Rockville Md is well equipped to deal with any lock issues.