Most of the time when a key needs to be jiggled or otherwise has difficulty nworking, the problem is a worn key.  You need to have a new key made.  Simply duplicating yours only results in a worn out key on new metal.  Using the code number from the lock, a new key can be generated back to factory specs.  That and a bit of synthetic lube in the lock will solve the problem most of the time.
Steve Sandlin
Steve's Lock Shoppe
'84 Wolfsburg Westy
'79 Bus
'00 News Beetle