I think that the answer is in your SOP. In my FCOM PRO-NOR-SOP-06 P 4/18 it says :
"The ADIRS outputs are used by many of the aircraft's systems: Set the selectors to NAV at least 12 min after aircraft power up. This is to avoid an incorrect date initialization."
Some msn are affected by this procedure, anyway try to set the ADIRS to NAV 12 minutes after aircraft powe up , this should solve your problem.
Don't see that in our FCOM's
Maybe they have changed it...