potterton puma combi boiler ,lockout red light comes on,often?

My combi boiler a Potterto Puma 80e works fine but is tempramental.After about 3-4 hrs the lockout red light comes on.After resetting works ok.When I use the hotwater tap, it makes a rattling noise only when I close the tap.This noise will last about 10 seconds.The water pressure is 1.5 mb.Recently it has been locking out regularly i.e twice in I hour.Now I can see a slight leakage near the tiny pipes inside the boiler.Can anyone help please.Thanks