Phil,
Thanks for putting the video up.
You are right, too far away and contrasty to check the flap positions. Having looked at the video I think this was a failsafe activation,as the roll rate was not excessive (as it would been with asymmetric flap) and the engine appeared to have throttle down by the time it hit the ground or it would have been far more comprehensively destroyed and probably have burned as well if the engine was still on high thrust. I think the tightening of the turn just before impact was probably when the engine shut down under failsafe and the aircraft properly stalled. The engine failsafe usually takes a second or two to kick in after signal loss, where as the radio gear on control surfaces goes into whatever failsafe mode has been set almost instantly and I think it was set to Hold last position rather than return to neutral. I would be looking at Tx battery or Rx positioning/orientation in this sort of event, might even be old DSM2 gear which can struggle when a lot of other Txs are switched on, as can happen at an event such as this.
Can't prove any of this theory of course but if I was doing a formal investigation into such an incident that is where I would start the search for evidence.
I would be interested in other (turbine experienced) members opinions, as I said to Phil yesterday I would rather learn lessons from other peoples misfortunes than my own!
Peter