I have two 30rbs-140 chillers using pro-dialog plus. They both flash an alarm "master/slave communication failure. I believe they have done this since commissioning, I'm sort of just walking in on this. The tech before me said the cable was too short. There is also a termination resistor on the + and - of the slave connector. I just tried to replace the cable with 20 meters of Belkin com cable. Same alarm. The resistor in or out seems to make no difference. Could I just have a programming issue. Im by no means an expert with pro dialog. Any other suggestions?