At no point does the AIController.Blackboard get cleared, once created. Which leads me to believe that you call your SetSubjectJobon something else than you expect. I’d double check that if I were you 
But if that’s not the case you can always use VS’ data breakpoint to observe changes done to AIController.Blackboard. If you find the pointer being cleared follow up in this thread, please.
Cheers,
–mieszko