The
reliability of the RR three-spool design is
very good, at least with my experience on the TriStar.
In sixteen thousand hours of flying the type, I have experienced one engine failure (flameout on descent due to a HS gearbox failure...repairable on wing in 6 hours) and two inflight shutdowns, due to high vibs.
Otherwise, no further problems.
RR builds mighty fine engines.
NB.
Also operated Conway and Dart-powered airplanes, no problems with those, either.