Inconsistent performance from motion sensor on doorbell

I have a Doorbell 3 Plus. Only had it a few days.I'm finding the motion sensor, for which I have set up zones to give me alerts when someone enters the driveway, to be very unreliable.I can't understand why, for example, the postman can walk up the drive and it detects motion. Yet I go out the front door, get in the car, drive off, and it does NOT detect motion. They are all covered by the same zones, and I have motion sensitivity set to high and motion frequency set to "frequently".By the way, this is NOT an issue of notifications, I do get them when motion is detected. It's an issue of motion not being detected when it should be (which I can verify through lack of recording).There just doesn't seem to be any logic to it.Any ideas?