SKS spontaneous unlocking after locking and exiting the vehicle

So has anyone experienced the following?

On several occasions, with SKS fob in pocket, I have parked, turned off the car, opened the door, locked the doors with the interior door lock button (on the panel, not the physical door lock), exited the vehicle and closed the door, and then right about the time I make it to the rear of the car on my way to whatever store I'm going to, I hear the unlock "beep" and all the doors unlock. Sometimes I'm more than a few steps away from the car. And sometimes I don't catch it, and come back to the car and find it's been unlocked all the time. It's like the SKS realizes I'm sitting in the car when I lock the doors, and maybe I'm too quick and it still thinks the fob is in the car when the door closes, so it unlocks the doors. But it's not the long "the-wife-stuck-her-purse-back-in-the-car-with-the-fob-again-even-though-she-knows-it-can't-lock" beep either, although maybe it's because it will let me lock the doors with a fob inside if a door is still open.

It's a mystery ...

 

Well, I'm guessing it's because I like pushing the other button ...

Please note I wasn't looking for a solution, just wondering if anyone else had experienced it or had a theory as to why, since the car is designed to function either way.