"Racal confirmed that the system was performing perfectly at the time of loss of power". Everyone says that after an incident............
Correct. Especially companies who define serviceability as working on their bench, not integrated into a complex avionic system within a complex aircraft, that in electrical terms resembles RF soup. Perfectly serviceable kit can give wrong readings because of external influences. e.g. poor bonding.
Sorry, been there and watched them squirm when "serviceable" kit failed miserably as soon as it was installed. (And then laugh and walk away as they realised the contract didn't include a demonstration of installed performance, as all avionics contracts should - but few are). Funnily enough, the worst example I ever saw was R****. The quote, as read, is meaningless.