It’s probably a plug in module on those small contactors. If one is open or missing it could be your problem. When I say scope the CAN channel I mean to look at the waveform with an oscilloscope. Compare it to the channels that aren’t getting faults and see what happens when contactors pick & drop, brake picks & drops. Does it clean up when one board is disconnected, etc. You could also run a logfile to look at next time is shuts down and see what’s immediately preceding the fault.