Interesting....
One time, I had a similar issue, where the bus voltage started at the operator, went back to the control through a long traveler for switching, (do, dc, nudg), and then back out through the traveler. By the time it got back to the operator, there wasn't enough voltage for the signals to be recognized. I installed "pull up" resistors, right on the operator, from the bus source, to each input. It just needed a few extra volts on the inputs, aiding the signal coming back from the controller, for the signal to be recognized. When the control would switch the input off, there was only a few volts idle on the inputs, not high enough to reach the switching threshold.
