Does not sound as though anyone is entirely sure what "it" is.

I've seen autothrottles disconnect as a result of the computer sensing N1 over commanded speed, but never have experienced an exceedence which broke an operating limitation (or even got close). Usually the triggering event for this mode is a low altitude level off or cut back, which Alaska might experience more than other operators. Never heard of such a thing leading to an exceedence. It is pretty easy to reach down and pull a thrust lever back, and we have immediate action items which prescribe just that action.

The CFM56 is probably the most reliable engine ever put on an airplane. It easily makes it's 30,000 hours on the wing.

In older designs the Fuel Controllers were limiting devices which reduced flow, leaving higher flow available in the event of a FCU or HMU failure to keep the engine running. Those would surge when a Fuel Controller broke or dropped off line. I think anyone with several thousand hours in a PW1XX series turboprop has seen that at least once.

Of course, this could not happen on a MD88. It has a FOC-U (First Officer Control Unit)