Brake clonks while reversing

This is common and is not a fault only a nuisance--it is because of the way the calipers sit. When in reverse, and you brake, the force on the assembly is in the opposite direction as when you drive forwards, and the small amount of play in the calipers make them clonk the other way. This also happens on Peugeots which also have the same assembly. Original brake pads behave better than cheap pattern ones.