Hi Raphael,
I just bought an original RockBand 3 and my wii is 4.1U softmoded and like you, when I try to start the game through disc channel I get blue screen saying 002 error. Now the question, you just update IOS 53, 55 and 56 and after that the game started through disc channel? Is your Wii still in 4.1U?
Thank you