Question is.. how many extension cords are you running?
as stated earlier, your appliance will require certain voltage to operate ( 110v) if in US.
Its important to cover voltage transmission quick ..
That socket has given up the ghost. It's time to replace the socket.
They make field-installable replacement sockets for extension cords.
If that particular extension cord is causing an undue amount ...
There are Warning signs everywhere not to use multiple power cords.
Your cord suffered current overflow leading to melting.
While the motor was running the Voltage dropped due to power cords.