In the past, they bang around the house to alert me that things are not right. I have gone to bed with the doors unlocked and they wake me to lock up.
Yesterday, they "broke" my garage door!!!!! I went to leave and the button wouldn't work. I tried everything possible and finally raised the door by hand to get the car out. My dad came to look, but since there was power to the opener but no sound to indicate it worked, we assumed the motor died on the 12 year old Genie. Standing in the garage, we were discussing going to buy a new system when my dad noticed that the bolts that hold the system and the door to the header were almost unscrewed (most likely from repeated vibration). Had those bolts failed when opening, my 11 year old would have been seriously injured. He lets himself in after school with the garage keypad and walks under the door as it opens.
I will forever think that my ghost children disrupted the motor until the bolts could be re-secured and made safe for their living brother.