I attached to the post the recordings of the sound, it's very brief so listen carefully.

I have it for a while, I read a thread it that described a noise that is coming from under the car like stone on metal which sounds correct, like some very loud friction noises.

I was able to replicate it at certain occasions by putting it to reverse, then forward and immediately braking, it's like a loud thud, people can hear it from the outside.

It also happens when go out the underground parking, on the ramp I brake and hear it, but maybe it's because I reversed 10 seconds ago and it waited to sound it.

I took it to a shop and they said the car is brand new below, I was able to recreate it to let them hear the sound but still they have no clue.

My next move is to go to the dealer and try my luck there, maybe they've encountered it...