Anyway, my point being, anybody who comes on here and suggests the mixing unit might need to be re-designed might not know the S76 very well.
SIK, NTSB and FAA has used GENHEL flight control simulator to simulate consequences in different scenarios. In addition they have had in use EASYY5/Adams Simulation software.
Accident investigators (Copterline 103) have had a possibility to follow these tests and also they had chance to make a simulated blockage (blocking pin) to the flight control system of the GENHEL. The immediate reaction of a blockage or a partial blockage has made pilot's flight control inputs to be illogical (pushing the control stick forward and helicopter is banking to the left, making the control stick move to the right the helicopter is pitching down....).
The certification requirements insist that the critical systems or components must be redundant systems or fail safe components. This could be an issue?
The S76B Sutton, 1986, Copterline 2005, Bristow 2015 has had similarities. Helicopters have come suddenly, without any warnings or cautions unflyable and each of these has had lateral spin to the right (collective up position and right pedal down due to Mixing Units mechanical couplings to compensate pilots work load for coordinated flight). All of these three cases have so quick and so confusing cases that none of these three accidents crew has not been able to make MAYDAY call...
It looks like the latest accident in Nigeria has had difficulties of helicopter's controllability? The NCAA together with Nigerian AIB will find out what is the root case for this accident. For sure something has went wrong, wrong badly but not deadly in this last case!