Hi Scotty and everyone.
I have a 2016 Smart Fortwo with 7100 miles that emits a clicking sound under the car when braking. The car needs to reach at least 185 Fahrenheit to start clicking, and it sounds like it's coming from underneath between the seats behind them slightly. The car doesn't jerk around when clicking, and it happens 40%-50% of the time when initiating braking upon reaching said temperature. The click can either be really quiet or very loud.
I took it to Mercedes-Smart and they were also confused on why this was happening. They updated the firmware and said to me the car may have "forgotten" how to shift properly. The 2016 Fortwo uses an automated manual transmission controlled by that software and Mercedes suggested it's optimized for stop and go city traffic and not longer country side driving (I called bull in my head about that). So surprise, the issue is still there the day after and I'm bringing it in again to them for another inspection.
Now, I have like 0% experience with cars, but I want to think it be something like the transmission or clutch. I have a web playable video on Dropbox below of the clicking. You can hear it between 21 and 7 MPH. Thanks for any help!