We had a waterproof Socket fitted in our Greenhouse by an Electrician and the first Socket burned out within a week so he changed it for a new one.
That was a couple of years ago, this socket was for a 3kw heater now when we tried to remove the plug we have found that the Neutral pin on the plug has melted the plastic on the socket.
What would have caused this? it didn't cause the fuse or the trip to go.
there was no sign of a problem until we went to remove the plug.