I can't speak to that as I get my car next Friday. However, I had a brand new x3 loaner yesterday, and while the car was nice I did not care for the auto/start-stop feature at all. Sometimes (rarely) it was smooth, and sometimes it was down right bothersome. That's not Ultimate Driving Machine worthy IMO. It just doesn't seem well thought out. When I turned it off the car ws much more enjoyable to drive.
We're you using this feature when you had the failure, and could this in anyway be related to the poor execution of Start/Stop? I'm curious, and I would have them fix it further until it is "right". Good luck
2005 325xiT Jet Black / Beige - current daily driver
2010 528xi Saphire Black/Black/Dark Poplar - retired
2008 528xi Saphire Black / Oyster/ 6sp manual - retired
2003 330cic Jet Black / Natural Brown - retired
2001 X-5 3.0 Titanium Siver /Black - retired
BMW CCA Member