I believe I read two of the sensors are LED so if the LED light in the sensor isn't being blocked AW thinks it's not on the wrist? Or perhaps the sensors are "feeling" the heat from your skin? If AW needs constant full contact (touching the skin), then AW would be very finnicky unless you wear it tightly on your wrist. I don't wear my watches tightly. If I rest my arm on the table I can see half the watch would not have full skin contact. Hopefully, that won't break the AW connection.