Back door open alert comes on, then key in vehicle alert comes on, then the door locks go on/off. Have had the problem since I bought the car but now is getting progressively worse and dealer has no idea how to fix/what is causing the problem. Hate to trade it in because has less then 60,000 miles.

 

Why don't you provide more details such as when issue happens ignition is on or off, any doors open or closed, key fob near vehicle or away from vehicle, etc ... the more details the better... then someone may have some clues and offer some insights....

 

First thing I would look to do would be to disconnect the back door sensor. Actually, before that, I'd unscrew and remove all of door locked sensors.
Vehicle will act a little odd, as it will be unaware that any of the doors that are open, but it will give you a data point to eliminate from the troubleshooting process.