I took an 8 hour trip this past weekend. I had a few instances of a slowdown. I think it is important to distinguish the different types for a slowdown (Phantom braking). For one, it usually is not phantom per se. The car interprets inputs and performs some sort of reaction to the situation. The user perceives it as phantom because we may not know what the car is reacting to. I try to discover the reason at the moment looking at all sensor input indications; car in adjacent lane, gps speed limit marker, collision warning, etc.
The most common and slowdowns I had were as follows.
Car perceived encroaching in my lane. There were several instances here. Some were legit and others were incorrect vehicle sensor input. The legit lane encroaching could be interpreted as unnecessary but IMO legit. We may as a human interpret the car reaction as unnecessary. But, it did happen and the car responded. In FSD scenarios, you would want this to occur when you are not paying attention. What I did like was the degree in which the car responds. It seems to adjust to the severity of the encroachment; slight slow-down to heavy based on the degree of the sensory encroachment. I had other instances of lane changes that need improvement by the sensors with incorrect sensor inputs and car reactions. When changing lanes, if there is a car adjacent to the lane you are changing to, the sensors and car sometimes thinks the car is in the lane and abruptly aborts the lane change again with degree of sensor encroachment. This is predictable. When changing lanes and a car is two lanes over, there is a 50% chance the car will think the car is encroaching on your lane you are changing to. I acknowledge the difficulty and prepare myself to take over.
Car gps speed limit geofence is flat out wrong. There are two scenarios here. One, gps fenced speed limit is wrong for the road you are on and slows down accordingly. The slow down can be perceived as braking but is just the car letting off the accelerator to achieved incorrect gps fenced limit. Second, flat out wrong fenced confusion. I was on a 75 limit interstate, when approaching an interchange there are times it picks up the limit of the other road you are crossing. The cars limit indicator changed from 75 down to 45 and then goes back very quickly. So the car slowed down abruptly then sped back up. There are times after the slowdown I could identify the limit confusion and other I could not. They really need to fix this one. They either need to start reading the signs or just do a better job of identifying the legitimate speed limit. I would assume this is on their roadmap to improve before FSD is implemented.
Incorrect collision warning. On my daily drive, one of the roads have reflectors as lane markers. When and if I change lanes in AP the car incorrectly responds to a collision with the sounds and indicators and prepares the car to brake. It is seeing the reflectors as a collision.
IMO, the car is responding to sensory input. I would not perceive any of the scenarios as a software bug (car is not behaving as software is intending). The term "bug" is normally incorrectly applied.
