Have been lurking for some time, waiting for the final report,
but one thing that stood out for me on initial scan was the
paragraph on the horizontal stabiliser, p218, 5.3.1.2, where
the concept of "pitch runaway" is discussed.
I'm sure that this must have been discussed at length elsewhere
in the topic, but would have assumed that any sensible system
design would inhibit ap engagement, or any autoflight function,
unless airspeeds are known good. Otherwise, feedback loop
with no null possible...