Getting back to the in flight fire scenario for those who have not read the Wikipedia on the SAA295 accident.
Quote Van Zyl took the voice recorder to the National Transportation Safety Board in Washington, DC, to show his goodwill and to ensure neutral observers.[9] Van Zyl believes that if he kept the CVR in South Africa he could have been accused of covering up the truth.[9] At the NTSB, Van Zyl felt frustration that the degraded CVR, which had been in the deep ocean for fourteen months,[19] did not initially yield any useful information. Around 28 minutes into the recording the CVR indicated that the fire alarm sounded. Fourteen seconds after the fire alarm, the circuit breakers began to pop. Investigators believe that around 80 circuit breakers failed. The CVR cable failed 81 seconds after the alarm. The recording revealed the extent of the fire.[9]un quote
Fire IMHO is still the most likely scenario