I have redundant SM811 with redundant PM865HI, redundant BC810 and redundant I/Os. One evening, suddenly all hardware undergoes to fault condition and caused a complete shutdown (No logs are available of that incident). After three weeks same incident repeated and logs are attached. We had to give hardware a reset to bring it out of the fault state and then perform a full download because program was wiped off. I am unable to understand how a fully redundant system can completely fail at the same time.
Please let me know the possible cause and solution of the problem to avoid such incident in future.