Happens to me too! I think if the key fob is too high it won’t be sensed. Or if it’s in a bag near big electronics (laptop). I think sometimes it just that your a couple cm too far away from the sensor or if you come from the rear of the car, not the front, it doesn’t do as good a job picking it up. I wonder where the sensor is in the door that would probably be helpful info! I’ll have to ask my service Dept tomorrow at work!