I'm late to the party here so bear with me.....you mentioned the alarm went off.As a M6 owner you would think to understand that when its 10 degrees outside, we weren't blessed with remote start. And Yes, this isn't the 1950s, but % vs % of stollen cars has only increases minutely in the last 64years in most locations in the Midwest, especially at 5:30am at the end of a culdisack in the burbs. Next how many times have you started your car and went back for something in the trunk? If you say you always pull your keys your just being hypocritical.
It happened again to my wife when she unlocked it at the store tonight, locked repeadly and then the alarm went off. Talked to dealership last week they haven't heard of it doing this. Also, I hate not to have an idea of what's happening because electrical grimlins are the most expensive type. Because no one checks that stuff anymore, mechanics don't repair they just replace til it gets fixed. That could be expensive.
Yes I know the car has a basic alarm but do you have an additional, dealer installed unit that uses a different key fob.
Dumb Q, but we/I gotta start somewhere.