Alcatel Unleashed

hello
I have a problem with my 4400 R10.1 that automatically switches to the cpub when it should be in STAND-BY and the cpua in MAIN, the 4400 restarts alone and the switch command is applied automatically. After reading the documentation I understand that it could be :
-a loss of clock (this is not the case)
- A bad disk sector ( I checked with the smartctl -a /dev/hda command but I don't know how to interpret the results )
- switch command requested by the system ( I never activated this )
-panel on the master CPU card
-IO2N board failure ( but how to check this please ??? a command ???? )
currently with TWIN command all is good I'm afraid it will reboot again

So the big question is why does it matter which cpu is main?? they should never many years ago named them A and B as long as the DB is in sync and netadmin is correct the system would run fine on either.,

A incvisu -B 1 on the now stand-by should give you a clue to why it switched