Why did it work before and not now? The extra copper might raise the melting point a bit but I would say your biggest mistake would be not running the magnetic pins separately. Most of these are made of Kovar, a 29Nickel, 17Cobalt, 54Iron alloy, whose melting point is 2640F. I would guess that the Kovar would be the last to dissolve and, therefore, there's enough Kovar in the material you tried to melt to raise the melting point beyond the capability of your setup. Also, you stopped the process too early, before all the base metals had dissolved.