I also just purchased this same model and I'm getting the loud "knock" when it starts and stops. It really startled me. My machine is super loud when it runs too. I'm nervous that there's something wrong with it.

Sorry about your experience. After several back-and-forths with Breville, including one that was not very nice, I got a straight answer. This is it:

"This noise only happens with the large bowl. I've tested our sample machines here many times and it makes the same noise as you are reporting. Unfortunately, there isn't a way to eliminate that noise while in use. The noise is coming from the blade and spindle when they first start to rotate."

So basically the noise is "the way it is." It does not occur with the 16-cup model; the difference between them is that in the 12-cup model the two main blades connect to the motor with the spindle (in the 16-cup, the blades connect directly without the spindle). I spent some time trying to decide if I could put up with the noise because I like everything else about the processor. But I decided that I would always be annoyed and concerned about it. It really sounds as if something is wrong with the machine. So I went through the hassle of returning it and purchased the Cuisinart 12-cup Elite 2.0 instead.

Yes, mine is new. Sounds just like what you said. Ugh

My loud clunking noise is when I’m using the small bowl for smoothies

Your ’Breville Technician’turned out to be ’Just Answer’ and it wanted me to pay $35 to sign up for ongoing subscription. Just devious the way that happened1