D3 if you apply the brakes hard while traveling at very low speed. I decided to try and capture video to see if there was a problem with the ball joints, instead it looks to me that the rear bushings on the lower control arms are worn. Is this much movement normal?
Some flexing in the rear lower control arm bushing is normal since it takes the most stress especially while braking. If they are flexing enough to get a knock then it is time to replace them.
A good test is to drive about 5 mph and hit the brakes hard. If you hear a knock then they are bad.