If the plug has melted into the socket then it will be down to a faulty plug socket not the washer.
As the pins inside the socket may have worn so with the plug pushed in it archs on the plug pins and this causes the burning and melting.
What you need to do is cut the plug top off the washer and just replace it with another plug and then replace the socket it pushes into.
It wont be a fault on the washer as if it was it will burn inside the washer and not the socket.
If you need anymore info just get back to me.