The most common cause of melting/burned terminals is a failure in the heating element. These often fail in a way that allows the heating element, which is encased inside a metallic tube with an insulating layer, to make electrical contact with the tube
Test an oven terminal block!
To check the terminals for power, turn the breaker or fuse on briefly and check the terminal block for power across all three legs. Then remove the power at the breaker fuse.
