Hello,
I would suspect the backplane of the chassis in this case. I do not think anything is wrong with the DAQ board because all channels of the 4 SCXI-1125's are multiplexed on 1 channel of the DAQ board. It would really be a coincidence when all for 1125 have the same channel defective.
I suggest, if the problem still exist, to get in contact with the local NI office to figure a way to solve this problem or to start up a repair procedure.
Best Regards,
RikP
Application Engineering
National Instruments
Rik Prins, CLA, CLED
Software Development Engineer