50mm lens "clacking"

Good afternoon:

just got my X-E1 yesterday and finally have the time to update the firmware and give it a workout...

I noticed that whenever I press the shutter button to start the autofocus... the 50mm lens makes a rather annoying "clacking" sound, and I traced it back to the f-stop blades inside the lens..

is this something you experience with your X-E1 as well or should it send this back to the seller?

Please advise - thanks

James..