Vietnam airspace had just been upgraded to latest ADS-B ATC monitoring. Flight data is downlinked twice every second. Where is the data at time of disappearance?
If I recall correctly (back about 50 pages) the last data packet reported 0 speed and 0 altitude which were obviously impossible but there must be an explanation.
I suspect the ADS-B transmitter had enough time to send just one packet after the sensors for speed and altitude stopped sending data to the ADS-B box which tends to indicate the sensors did not fail from the exact same cause as the ADS-B box.