First post here and let me state that I'm not a S-92 man and certainly not an electrician so this is only theory - not trying to state facts.
In regards to the CVR/FDR electrical interruption I believe there are 2 AC generators being driven by seperate input modules which are attached to the MGB. Lets say the MGB starts to slow down (failing), wouldn't this also cause the generator to slow? If so the generator control unit would sense an under frequency and shut down both generators- no more AC power!
Like I say only a theory and I would welcome enlightenment from anyone directly involved with the S-92.