JMHO's here.
I know the GE is a different engine, but both RR fadecs and GE fadec software versions go through the same flakey FAA appoval process.
Air Safety Week:
Trouble-shooting technicians have found that the two cases in which there were single-engine thrust reductions during takeoff were the result of a flawed software algorithm in the Full Authority Digital Engine Control (FADEC). ....
....Others might wonder how such safety critical software can make it through the validation and verification regime into world-wide fleet service. Overall, it's shades of the previous GE90 "rollback" and IFSDs (inflight shutdowns) from earlier days. The only difference was in those cases, it was in cruise and was caused by moisture freezing in the P3B and PS3 lines to the FADEC, and it was resolved by increasing the tubing diameters....
Lots more here at the source; worth reading:
Air Safety Week :: The Unthrustworthy 777
pac