A320 question about flaps vibration

[KrisK]

Hello,

I have a question about the trailing edge flaps on the A320.

I was on a flight this morning. During approach with the flaps extended I noticed the outer trailing edge flap was vibrating. It almost looked as if the flap was loose at the point where it is attached to the wing. It went approximately 3 to 5 centimeters back and forth. Only the part where the inner and outer flap meet was shaking. There was no turbulence. I know that flaps are not fully extended during takeoff but I don't seem to recall seeing any vibration after departure. Is this kind of vibration normal? I have never seen flaps vibrate that much.

Thanks!