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).
Those particular Wessex (ex 28 Sqn if I’m thinking of the same five airframes) suffered very poor serviceability in the latter days of their RAF service; it’s hardly surprising that engineers with far less experience had trouble with them.