IMHO a temperature rise of 20 degrees C to minus 34 degrees C at 41,000 ft can only be explained by assuming an anomaly of the temperature sensor.....
not so sure about that, in fact there are known cases, especially from aircraft crossing the ITZ, were exactly such a SAT temp "anomaly" happened, due to convective action BELOW the aircraft's flight level, which in fact had created havoc with the engines and the flight path...in one case a G-IV experiened unstable engine ops ( I think it was a compressor stall) and departed controlled flight in a gross upset...