Try this Field Inspection procedure on the fully assembled
and unloaded pistol before contacting Glock customer service:
Excerpt from Glock Armorer's Manual, ęGLOCK 2009, Page 64:
Firing Pin Safety Release (free movement)
When the trigger is pulled, the firing pin safety moves upwards and clears the firing pin channel to allow the firing pin to move freely to strike the primer with sufficient force. With an unloaded pistol, point it in a safe direction and pull the trigger. Hold the trigger rearward and shake the entire pistol. You should hear the firing pin moving forwards and backwards. This ensures the firing pin channel is unobstructed and the firing pin safety has been moved enough to allow the firing pin to move freely.