The heat is the cause if it is close to the element ends of the heater. The twist is normal, the plastic insulation is swollen and deformed. The wires are twisted as this creates a shielding effect to reduce magnetic fields, it adds cost as more wire is needed for the same cable length, normally you cannot see the twist. The motor is only an electromagetic, it does not and cannot spin. I have seen this a few times and in past cases the cause was always a long soak in muriatic acid or similar strong acid or running them in a small amount of water that got very hot. How old are they? I would agree that they are not safe to run, the PVC insulation is swollen and soft and could be breached.