F15 X5 50i MY2018 41k milage, still in warranty.
Mine has this issue as well. sometimes the sound syncs with engine when rpm in the range of 1k to 2k. Only a few times, it sounds normal. I Went to dealer twice, they said it's ok and no problem needs to be fix, then I asked my friend works at dealership who's in china. He replied "This is a common issue of F15, no way to fix." He implied that this reply is from BMW official tech support.
Will mark this thread to see if there's a way to fix this annoying issue.
