In nearly 6000 hours of flying with the Gnomes in Wessex and Sea King, I had one partial rundown and one real computer freeze so I'm pretty happy with their reliability.
I flew with the FAU (Uruguayan Air Force) a few years ago and they had a dispersal full of old Wessex we had sold them many years before. They had had such problems with them because they didn't know how to set up the fuel computers that they became impossible to use (no manual override on a Wessex).