Hi rh71,
I have exactly the same situation as yours. However, the BMW does not admit it is an issue or problem. I don't remember I had such creak during the first year of ownership (or at least the first half year.)

I think the techincian do not even know what it is or what causes it, so they just try to fool me around until the warranty expired (this September.)

I just leave some record in their log so that in case in the near future they tell me that I have suspension problem or something similar, I can argue with them.