Having taught some FADEC systems, I was never overly-confident when I heard from the 'nerds' how much 'stray code' there was resident in the software.
FADEC has been around for literally decades on a wide variety of aero engines. C-17 for example has FADEC engines and fly by wire throttles and it's an over 30 year old design. There is absolutely no reason for a FADEC design to be unreliable.