missing person

I've found on more than one occasion that the ring doorbell has a mind of it's own. Selective recording maybe, i tried my theory tonight we came home and was on our history as person detected but an hour later we had food delivered and it didn't see the car pull up or the delivery man stood right in front at our door. No alert received or any video history of him ever being at our front door how is this possible it's scary as if this was an intruder I wouldn't have any video recordings of the incident the main reason for the purchase of the doorbell in the first place