BTW, has this clatter got worse as the winter has come on with lower temperatures? I assume you are on summer tyres, which can harden up a bit with cooler temperatures and that can give more issues if the suspension is already struggling to give good ride quality on poor surfaces.
Been there with the E91, so have a bit of experience when tyres just don't work the same in cooler temperatures.
I'm on Adaptive Drive and running 17" winter tyres. There is a slight difference in ride quality as the temperature drops, but the suspension still does pretty well. As I'm in the touring I have the benefit of rear air suspension, that helps sorts the rear out as well with its variable spring rate. I sense every little helps to cope with using RFTs.