KG86
You mentioned:
But, in all my Chinook experience, I have never heard of another such event.
I am surprised that you have not heard of the US Army Chinook's UFCM in June 1997 when one of their acft failed to respond to a control input, rolled in the opposite direction and eventually rolled through 180 degrees before control (of sorts) was regained. In the process, the Chinook descended from its cruise height of 1100 ft to 250 ft, following which the crew landed (untidily) asap. Despite extensive engineering efforts, no fault was ever found with the acft. Hardly surprising, therefore, that if no fault was found on an intact acft, it is unlikely that a similar technical fault would have been found within thenwreckage of ZD576.
I also have a document listing 35 separate UFCM events between 1994 and 1999.