The DMX input on port 1 of the RNC works fine, but the input on port 2 is not outputting correctly.
First step: make certain within the Setup menu on the RNC that you have the two input ports merging into one output. See the manual for this information.
If the correct settings are in the setup menu but the problem continues your next step is to consider:
Port B input on the RNC starts at 513 within the RNC's patch. As we all know, there is no such thing as a DMX value above 512. However, within the RNC it is very similar to the patch on a console. You can patch dimmers 513-1024, but you know that this range refers to the second universe of DMX from the console. The RNC does the same thing. Within the patch of the RNC, input port 1 refers to values 1-512 and input port 2 refers to 513-1024. Therefore, if you have two consoles inputting into the RNC, you will need to patch the incoming values, within the RNC, on input port 2, with an offset of 512.
SEE ATTACHMENT: Response Network Controller Manual