Hi, I’ve just bought a 2022 plate A3 S-Line, manual, and think I have the same issue. Only had it a week and it’s running fine, except when I brake at very low speeds I hear a grinding sound, possibly from the rear brakes, not 100% sure but seems like similar to as the OP says. I also think it becomes worse as the car warms up. Braking at higher speeds seems fine, it’s just a grinding sound at very low speeds. It’s booked in to be looked at in a couple of weeks as the dealer said to pop back with any issues. It also creaks at the back when reversing on a bit of an incline, then breaking and then starting off forwards. I’d be interested in any updates from the original post? Thanks.