Originally Posted by
Bergerie1
but it does not explain exactly how and where the fuselage was distorted
I have never found an account that linked one to the other, but according to most accounts the distortion wasn't found until after the testbed's final flight and the reverser incident would appear to be the most likely suspect. There is a firsthand account of that flight here:
https://www.vc10.net/Memories/Testflight.html
It could also have been the result of asymmetrical weight, drag or something else, but I haven't found an answer yet unfortunately.