I am glad to see that you intend to get to the bottom of this and stick to the original story. It would be interesting to hear the other side of our national airline.
In the original post a date is given and it was within a certain FIR. This would narrow it down somewhat.
Is this sector, somewhere in the middle of the flight, during the Captain rest period which would leave an F/O resposible for the alledged argument about descent! Could this possibly be?
