BOTH REAR SLIDING DOORS ARE NOT STABLE WHEN MOVED TO FULLY OPEN POSITION, ESPECIALLY ON ROADS/DRIVEWAYS WHERE THERE IS A DECLINE. IN FOUR CASES OVER THE PAST TWO WEEKS, THE VEHICLE WAS PARKED IN OUR DRIVEWAY WITH APPROX. A 15% DECLINE. I OPENED THE DOOR FOR MY SON AND IT "LOCKED" IN THE FULLY OPENED POSITION. HOWEVER, IN ONE INSTANCE HE WAS EXITING THE VEHICLE WHEN THE DOOR CLOSED AND LODGED HIS HEAD BETWEEN THE DOOR AND THE FRAME OF THE VEHILCE. HE WAS NOT SERIOUSLY INJURED. SIMILAR THINGS HAVE HAPPENED OVER THE PAST COUPLE OF WEEKS.. WE ARE RENTING THE VEHICLE FROM ENTERPRISE. I BELIVE THAT A VERY SERIOUS SITUATION EXISTS AND SHOULD IMMEDIATELY BE INVESIGAGTED. WE HAVE RENTED OTHER MINIVANS IN THE PAST, AND ALL HAVE HAD ACTIVE LOCKING MECHANISMS WHERE THE HANDLE HAD TO BE LIFTED TO CLOSE THE DOOR. THE WINDSTAR RELIES ON A SIMPLE DETENTE WHICH IS NOT SUFFICIENT FOR VEHICLES ON DECLINES. *AK