Old fashioned thermal heat transfer from ohmic heating.So the consensus is Loose wires, however a question - How is the burning caused on the socket interior? Via Arching?
What else could it be caused by?
https://www.hunker.com/12609342/why-do-appliance-plugs-get-hot
https://reference.wolfram.com/language/PDEModels/tutorial/HeatTransfer/HeatTransfer.html
