SAS
the engine problem and the flight control problems did not have a common cause as they are two very different systems.
However there is a place where engine governing meets flight controls - the anticipator, which is a pair of potentiometers that set each engine's N2 datum, and therefore have the power to cause the sort of engine fluctuations they experienced. The anticipator is located in the flight control cabinet and whilst its connected only to the collective pushrod, its adjacent to the cyclic pushrods.
Despite my feeling that this must have been the common link, the investigation found no evidence that there was any connection.
HC