As I have tried to explain before, don't get hung up on the ARS6/PRC112 issue - it is only a suggested candidate system that I think fits.
What is important is that you with experience of the contemporary avionics and practices come up with a plausible explanation for the handling pilot's HSI course selector being on 035M.
This was the line from the position of waypoint change to the crash site; he would have had 027 set for the previous 40ish miles to that point.
What could he have been referring to?
Either an external radio aid of certain types or a waypoint in the SuperTANS can get your CDI working usefully (otherwise why change the course setting?).
What do you suggest?