My hypothesis is that since the sensors are not lightning up, it's likely an issue with the main PCB, rather than the motor PCB? I can test the PCB, although I'm not specifically sure what I should be looking out for. Documentation on this device is sadly somewhat scant. Any tips would be gratefully received. It occured to me to check the output pins to the IR LEDs and the motor PCB, although I'm not sure the pinout of the latter. Also not sure what the normal voltage should be.