I just had this vision of one or two plastic flatcar(s) with plastic trucks, with one center roller and one wiper on one of the axles of one of the trucks. So two hot wires from two different center rollers, and two ground wires from two different axles. Then, there is a matrix of LEDs with resistors that will some how indicate which of four just went dead. What happens with two, three, or four go dead, not sure.
Meanwhile, never hurts to clean the outside wheels on your loco - got burned by that with a Atlas GP60 with rubber band tires on the inners. Also had an Atlas dummy that the connection to the outside rail was thru the frame to truck connection, and it didn't always make, so I ran some jumper wires and tied the frame and two truck frames together.
I have a hard time seeing an E-8 having that problem but you never know.
