[sswee]

Without some details, can't say for sure but it is most likely one of two things. Either a bad connection or too much current through too small of a wire. With both you will have a high resistance causing the voltage to shoot up trying to push the current through the circuit and excessive heat generated at the point of high resistance causing the burning or burn out.
You would not have gotten enough current past the point of the resistance to anodize. That is why your dye only took where it did. On parts that loose connection during a run, the hanging wire will take dye up to where the connection is lost.
SS