If anyone has arrangement illustrations of the tail drive and control system, it would be helpful. One thing jumped out to me was the shearing of the TRDS section 3 being missing, with only an end cap found with sheared rivets. If by 'end cap' they are referring to the end portion of the drive rather than an environmental cap, then shearing rivets could be a sign of torque overload as well as simply being ripped out. The direction of loading on the rivets, if indicating rotational, can be a clue. Like these all are, the challenge for the investigating team is to determine what fractures preceded others. Troubling that they have not located one bearing and a shaft.