If it was due to compromised heat shield, the rise in temperature should have occurred as soon as they started coming into the atmosphere (above the Pacific), not suddenly during later stages S curves. They have already slowed down from above 17,000 Miles/hour to 12,500 miles per hour. if the defect was due to the foam piece hitting the left wing, that would have started heating up as soon as they started slowing down. Furthermore, the damage was far from the wheel well but the temperature rises and pressure loss in the tire were noticed as first event of malfunction, possibly a small charge or a slow acting chemical hidden long ago within the tire so no inspection could discover it.
Zeev