as I had a similar problem with no air from vents, I investigated further on my car and we found no broken stepper motor mount, but the stepper motor did not hold in place with the clips, so we fixed it with zip tie, works like a charm now.
Have made a youtube on my spare IHKA unit to show how the flaps work

How it works aircon top flap control - YouTube

Stepper motor IHKA picture by shogun_bucket - Photobucket
Applies to defroster flap and temperature regulator flap, 2 actuators per car

stepper motor IHKA picture by shogun_bucket - Photobucket
Only applies to leg room flap, rear flap, air re-cycling flap and fresh air flap. Six actuators per car

http://www.bimmerboard.com/members/h...m%20holder.jpg