Sorry I wasn't clear.
Inside there is an electromagnet and a set of double points.
Underneath, there are resistors.
There's also a fuse wire.
Look at which one failed. This will be the first clue as to what went wrong.
Aah ok, the points had welded themselves together. And then naturally the fuse wire.
The fuse wire runs on the inside between one side of the points to the resistor, correct? And there's one on both sides of the breaker points?