I wired in a new freestanding electric cooker and it blew the electrics and left black scorch mark on the live wire. I wired the old one back in, this was fine and when tested by turning on a plate it was still fine. I turned off at the mains and screwed the cover back on but when I turned the electrics on, the same thing happened there is black on the live wire again. With the cover off it is working fine. I should add that when I first removed the cover plate I did notice there was only 1 screw holding it in place and I am replacing it with 2 in place. Why is replacing the cover causing this to happen? I obviously don't want to leave it with the cover off and wiring exposed.