Based on how the sensors failed, I can see now why they'd be focused on the elevons. It appears that the failures started there, and propagated sort of forward and inward.
One possible culprit might be the hinge area -- a good ding in the tiles thereabouts might cause problems there and propagate inward.
Of course, we're assuming it's a thermal protection failure. The right kind of hardware failure might have a similar effect. For example, suppose a hydraulic line burst -- it might kill sensors, loosen tiles, and there you go.....