the system works off pneumatic lines. When one of the lines breaks the lock doesn't function. I had this same thing happen to me. Came out from the grocery store and the hatch was unlocked. You can hear the air going through the system when it breaks. I took mine to the dealer to be fixed, although there is a "kit" I've seen in a thread here. You first have to find the point where the line is broken. Didn't look too easy to me so I let the warranty take care of it. I think finding where the break is is actually harder than repairing it.