The rear liftgate on my dad's 2011 Yukon will not open any more. He's had a problem for awhile with the auto lift portion of it (I think the lift rod popped off of the piece that rotates up on the motor), and now neither the button on the tailgate itself or the remote will pop the latch on the gate. The window button works with both the remote and the external button. I'm assuming that either the door latch or some kind of actuator needs to be replaced, but I've never been inside a liftgate so I'm not sure what all is in there. Anyone have any ideas?