I see the loco hauled services most days (they pass my house). Yes, punctuality has been a problem, but it seems to be more a case of turnround times that are so short, if a train gets delayed a few minutes, it cannot recover, then with sigle line sections, things only get later and later. There have also been some signalling problems too. Hence I don't think reliability/punctuality problems are due to them being loco hauled sets rather than dmus.