Last week I took apart the face plate off the electrical wall socket and sure enough one pole was blackened and sooty. I removed that wire and 5 of the 6 copper inner wires fell out leaving a single 1mm strand of copper. Either the original electrician cut through the wires when he stripped the insulation off or when he screwed down the wire the nut cut through.
Ok so I replaced the wall socket and re-strip and reseated the wires but as soon as the range was plugged in the breaker trips! So either they bad wiring caused the range to be defective or it was a coincidence.
New range arrived today and it works fine. Self clean too.
Thank you all for the great advice and help.