Against  Void  Affinity  -  The  Boss  should  Target  Aox
Boss  is  Neutral  when  Void  Affinity  +  Everyone health  is  fairly  close
The  Leader (Aox) should  get  the  Stun  Hit
Against  Force  Affinity  -  The  Boss  should  Target  Frozen  Banshee
Boss  is  Strong  against  Magic  when  Force  Affinity
You  have  2  Magic  heroes  on  your  team  FB  +  Ninja
FB  Health  is  lower  vs.  Ninja  Health
FB  should  get  the  Stun  Hit
Against  Magic  Affinity  -  The  Boss  should  Target  Iron  Brago
Boss  is  Strong  against  Spirit  when  Magic  Affinity  +  Iron  Brago  is  only  Spirit  on  team
Iron  Brago  should  get  Stun  Hit
Against  Spirit  Affinity  -  The  Boss  should  Target  Skullcrusher
Boss  is  Strong  against  Force  when  Spirit  Affinity.
You  have  2  Force  heroes  on  your  team  Skullcrusher  +  Aox
Aox  is  leader  +  has  lower  health  vs.  Skullcrusher 
Under  normal  situation's  Aox  would  get  hit  with  Stun.
The  problem is  the  Clan  Boss  is  redirecting  his  hit  to  Skullcrusher due  to  Buff  Expiration.
Iron  Brago  places  Increase  Def  on  team  for  3  turns.
Everyone  on  the  team  keeps  it  for  3  turns  except  Skullcrusher.
It  is  because Skullcrusher moves  last  on  the  team.
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Based  on  your  Hero  Stats  +  Clan  Boss  Behavior I  observed for  3  years,  I  think  some  of  your  problems can  be  fixed,  but  not  all  of  the  fixes  will  be  the  way  you  want.
To  Avoid  Skullcrusher from  being  the  Stun  Target  when  Spirit  Affinity:
You  would  need  to  make  Skullcrusher faster  vs.  Iron  Brago
or
You  would  need  to  make  Iron  Brago  slower  vs.  Skullcrusher 
or
You  would  need  to  delay  Iron  Brago  Increase  Def  Buff  by  1  or  2  turns.
To  Avoid  Iron  Brago  from  being  the  Stun  Target  when  Magic  Affinity:
You  would  have  to  add  another  Spirit  Hero  to  the  Team  with  lower  Health
or  
You  would  have  to  completely remove  Iron  Brago  from  the  team
Lastly,  Frozen  Banshee  isn't an  ideal  Stun  Target.
FB  can  do  more  damage vs.  whole  team.
You  don't want  her  losing  any  turns  due  to the  Stun.
You  would  want  Ninja  eating  the  Stuns  or another  Magic  Tank  which  you  can  swap in  place  of  Ninja.