It wasn't a disc failure, and it was aileron, not rudder, but QF30 (the 747 oxy bottle depressurisation) had its starboard aileron cables cut. The effect of that was that there was no roll control from the starboard wing. But, nicely positioned on the other side of the aircraft, there was a second cable run for the port side roll control. From the cockpit perspective, roll control was sluggish, but otherwise pretty normal.
So, cables do get cut, and properly designed backup can neatly resolve it.