I have a 96 850 T5 which has an annoying habit of unlocking itself. sometimes it is immediatly after locking (either with key fob or manualy with key) and sometimes I return to the car after a couple of hours to find its done it again.
I had the same problem last year when the winter weather arrived so I suspect damp / cold weather is affecting a connection / earth somewhere. is this a common problem? has anyone had it before it would be intresting to know before I start searching for culprit. thanks

How old is your son and how ingenius is he?? Maybe he built something from RadioShack and is playing with you!!

It doesn't take much to activate the "lock", "unlock" circuits on the fob. Sometimes just a simple tap of the button, for example putting it in a pocket, wil activate the lock. Why not check to see just how little pressure is needed on the fob to unlock the doors, and if it seems a little sensitive, I'm suggesting you pry the fob open and clean the contacts with electronic contact cleaner.

troubleshoot by removing the remote and keep it out of distance from the vehicle. Drive the car a few days with using only the key to unlock/lock the vehicle. If the car no longer mysteriously unlocks on its own then its a problem with the remote. If it still does.. then its an electrical problem with the car.