I've heard about this issue but the information available is all over the place. I've heard certain years after a specific production date are not affected, that BMW extended warranty, etc.
https://bmwtechnician.com/2016/08/07...g-chain-issue/
https://bmwtechnician.com/2017/08/02...-bmw-bulletin/
http://www.rightfootdown.com/cars/au...nents-n26-too/