I don't know if you've figured out your alarm problem yet but I went through a similar issue and here's what was wrong with my X5. My right rear lock actuator was found to be faulty. So they replaced the lock assembly. They also found the module faulty and replaced that too. Did the trick. No more random triggering of the alarm all night long The items replaced were:

51-22-8-402-602 MOTOR ACTUATOR
65-75-6-928-429 MODULE

Anywho, hope your dealer did you justice with your baby

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2005 X5 4.4i with SP, PP, CW, RC, Prem Sound, DVD Nav, Comfort Seats, Style 87 Wheels, Alum Running Boards, Sirius Sat, 6-cd Changer.