So you are saying the modules connect to each other and have comunication via the signal path PSC-->TX-->RX (and back to the PC)? Is it possible (or have you?) to connect a second PC to the RX and have another instance of X-CTU monitoring that data get through? If this is positive, start with the VOLA-SW pushing out data and see if RX still receives. My guess is you are missing a link in the serial path.