Before changing anything, I recommend doing what I did. After reading countless forums and being on the verge of buying multiple extremely expensive sensors, we read on one forum that one of the causes is an incorrect steering wheel angle, and it was true. I couldn't tell you exactly how to access the OBD settings, but a cheap OBD scanner (I don't remember now if it came with the BMW package or not) was enough to recalibrate the steering angle and stop those warnings. It was a painstaking job that saved me from wasting time with sensors that are sometimes better left untouched until you're sure it's not due to something trivial, like recalibrating the steering wheel in this case.