So it turns out the system is designed and manufactured near to me in the U.K. and it might be worth contacting them directly with consumer feedback in relation to any drone issues, especially as they claim "the clear target from BMW was to deliver acoustic performance fitting to the extreme sporty nature of the vehicle, without unpleasant resonant frequencies"
http://redarcheng.co.uk/news/bmw-m2-...duction-ramps/