Hi Gents, Ladies,
I can't remember if it has been mentioned before and I can't see it anywhere, but with the acknowledged 'dodgy CAD', could it be that the numerical fuel indication was somehow 'tripped' to make it show in lbs and not kgs?
"CPDS
A fault relating to one of the display systems was recorded and further work is being undertaken to establish the meaning and possible causes of the fault."
In this scenario with 47/43 lbs indicating, there would only be 21/19 kgs in the tanks. By the time this may have been fully, if at all realised and the warnings came on (late?), a dirty dash back to base may have been the only reasonable course of action at the time.
Just another thought