Hi, The issue is with Redundant CI840 Module. Following may be the causes: 1. Hardware of CI840 (either one of redundant CI840) is faulty 2. Baseplate of CI840 module is faulty. 3. Profibus connector or cable may have functionality issues. 4. check field alerts for current firmware of your CI840 module.
You can troubleshoot further if you have profitrace tool. additionally you can check logs of CI854 Master.
Perhaps this is shot in the dark. I have been facing similar issue. Finally we found the problem in the baseplate of CI840 at micro switches, which are touching screw tip of each CI840. There was a small metal stripe of micro switch flipped in wrong position. Metal stripe should be located on top of each micro switch. This fault was indicated by red LED on CI840.