I have never known them to randomly open unless the key was press for around 5 seconds (i think its about that long) i used to use this feature in the summer and let the heat out before getting to the car. I used to get this at work where the key was in the pocket. luckily people left it alone
Whats the condition of the key like? sticky button on fob?
You may get round the dealer, not 100% sure but sometimes there is a procedure you can do to disable it, I did it once with the seatbelt chime.