Only thing I can think of is if the door pin in one of the doors isn't triggering to tell the car the door is fully closed. Does your dome light circuit work when you open the door? Indicator on the dash say the door is open? I know with the oem keyless entry it won't lock if the door is open..not sure about the hatch but maybe start investigating that. That's all I got
Like the guy above me said, check your doors. Also check to make sure your hatch is closed all the way. It'll keep you from locking up as well. Just went down and tried mine with a door closed but not all the way and it's doing exactly what you're describing.