Wow. It took them a while to find that one for you.
I was a lot luckier with mine.
My steering was making a small noise on delivery.
Within a couple of weeks I took it back and within the day they decided to replace the steering rack.
Another three week wait for the parts to come from Germany then they replaced it.
Happy to say that I did not have your symptoms though, with either of my steering racks.
What I did get was a shock at the price. It was a $5K fix for the car, and that is with the internal labour and parts rate that BMW pay their dealers.
It never ceases to amaze me that they did not flinch at paying the $5k to fix the steering rack noise, but they refused to pay the $30 for the three wheel hub caps that fell off the car the first time I drove it on a track.
2010 Z4 35is
2011 X3 30d M Sport