The cause of this overheating may be the result of shunt feeding the tower for 160m and not grounding the insulated element of the XM-240 driver at the feedpoint when xmit on 160. (ie. short out the balun).
It's hard to believe there would be this much common mode current on 40m !!
Top view...looks ok from the outside.....(but under the label it is melted)
The bottom of the box appears melted from the outside, and the inside top has been damaged from contact with the over heating torroid stack.
The teflon coax cracked from overheating and melted plastic from the box lid is stuck to the torroid stack.