Taiko no Tatsujin 7 confusion!
Mechagai gave me some instructions in that thread on how to open it up and stuff, but the problem seems to be different to yours... I don't think 'cleaning' it is really going to do anything. If your tatakon is registering hits when you don't hit it then that means a sensor has come loose, but I don't think that should happen with the middle bit.
Sorry I can't be more help.