What all is in the loop? If it’s all S24-1 boards, get one and replace each, one at a time. Also, how did you verify the cables are good? Most plug in testers will only catch a bad cable that’s actually open. Replacing them is the best way to be sure. I made a little tester with 2 breakout boards that jumps the pairs together on one end so you can check resistance of each loop from the other. Those kind of bad cables usually show up as one loop measures 1 or 2 tenths of an ohm more than the other 3. And you did the TECC after replacing the CN right? It doesn’t know how many ports to look for until you do.