When using the old Controller module (ATmega128) and version 5 Communication module following modification have to be performed to avoid conflicts of MAX232 drivers.
It is necessary to disconnect the MAX232 driver Rx1 on the Controller module. By using the soldering iron heat the pad 9 (see picture below) and bend the pin up with a small screw driver. All other pins of the MAX232 driver can be left as they are and in case of later need the disconnected pin can be easily connected again.