Vovachan; lonewolf, re “assumed ALL instruments were suspect/wrong”, but ‘not likely’.
Not likely, but don’t discard the thought. See another
A330 Incident where unreliable airspeed (pitot probes freezing) resulted in an apparent change in altitude (assumed low speed correction factor). Also, note the effects in the erroneous change in TAT (TAT probe freezing). What haven’t been established so far are the effects of ‘rapidly’ changing speed and temperature on other computations in the ADC and possibly in the IRS module.
If the crew’s perception was of a ‘failure’ of airspeed, sudden drops in altitude, and perhaps rapid changes in VS, then concluding that there was a ‘display’ failure (the computation behind displayed parameters) would be logical.
xcitation “Also stated was air temperature increase which indicates updrafts and turbulent weather”.
The ‘increasing’ temperature could have been due to the TAT probe blocking with ice crystals, again see the A330 incident above.