FWIW, I changed both of my solenoids this weekend. I accidentally started the car w/o plugging in the electrical connectors and the car ran fine, in fact, it was quite smooth, and the marbles in the can sound disappeared. It instantly flashed up a yellow half engine light though.
But when I plugged the connectors back in, the marble sound is still there, but substantially reduced. But I have a feeling that changing the solenoids isn't the issue of the marbles in a can noise because it still present.
E90 LCI M3 7-DCT Interlagos Blue/Novillo Silver
[MS Pullies|K&N drop-in|Test Pipes |Evolve Stage II tune|Evolve Servotronic Map|Evolve M3 GTS-DCT file]