So I have driven my 2017 AP2.5 75D for more than half a year. It's the first time I saw this behaviour (and I updated to 2018.21.9 only a couple days ago): I was driving on a stop-n-go expressway in the morning with good weather conditions with autopilot engaged (following distance 3). The car in front of me made a relatively rapid deceleration - nothing too panicking. AP detects the slowing down and applies brakes rather quickly. The brake paddle makes a shuddering/thump/pulsing sound (which I have heard quite often before during rapid slow down by AP, which I think is normal). However, what's different this time is that right after hearing that sound, the AP just canceled itself! At the time, the car was still moving slowly forward. I had to take over and apply brakes further. And when this happened, the car only made a normal AP cancellation sound, no warning sound/no warning texts. I'm not sure this is a normal behaviour - but I doubt it. It's the first time I have seen this. It feels as if AP was applying a little bit too much brake force to the brake paddle that triggers the AP to cancel. I would consider this a safety issue as AP would just cancel without either human intervention or proper warning after it did that.