[suicideneil]

Cold solder joints where the bullet connectors ( motor > esc ) are attached to the wires; the solder melts inside the cup just fine, but it doesnt stick to the metal. If you tug the wire, it comes out with a cup-shaped plug of solder on the end and the inside of the cup is clean as a whistle inside ( like a cup of ice- warm the cup and the ice drops out in one solid lump ).

Otherwise I'm fresh out of ideas..