Surprise, surprise! I changed to a new rx/tx and plugged in the one remaining working light and it works fine, with no interference when I turn the wheels. So I have one light happily 'rotating/flashing', and a new set on order to replace the shorted out one. Haven't got the 3rd or 4th channel to control the light's flashing yet, but that could be my new radio learning curve; or the damage I did by accidentally reversing the polarity.