We've done 3 different systems with 2way on the CT600's with no problems. The systems we have done were all via TCP/IP. It seemed to make it easier once you have a network connection you can communicate to it with the xp8 or configure in bksuite from a laptop without having to connect the serial cabling in and out. When you swapped rs232 ports, did you just change them at the xp8 ports or did you swap them from ct to ct? If at the xp8, you could have a pin configuration in the DB9 or RJ45 or a cable continuity problem.