Okay my theory of why goes back to the tools that we have a available for locking the cams. Most of the tools used to lock them are aftermarket, where as the BMW is more robust and far more expensive. These engines are very particular when it comes to timing. Like I said its just a theory. In March of this year I had my X5 ripped down to do the usual timing chain guide replacements, timing chains, whole 9 yards etc.) When we were done putting it back together she was timed spot on with the tools that I had. All seamed to be good and then after 275 miles of operation timing code was triggered. Scanned the vehicle and I cant remember if its was over advancement or over retardation but the cord was there. Everything lined up great after competing the timing re-check. This time around we went back and reset all of the adaptations and drove it again. That was over 3000 miles ago. So there is always something new on these vehicles but they are finickier than the average V8 engine when it comes to timing.