unexpected action (not firing a crossbow)

[Pocus]

hi there,

I have a guy equipped with a vision foe. Its first round and the script is Fire on first round (he is still alive so I'm sure!).
Defender move, and some of his flyers attack my main force.

Then, to me. First round too, but on the attacking side. My main force surround the 5 enemy flyers, but dont attack yet.
Then my xbow guy move toward the rear of the enemy, and strangely dont shoot at anything!
Next action is that my main force dispatch the 5 enemy flyers.

So I wonder why he didnt fire on the 5 flyers. They were in range, all lights were green! The only thing I can think of is that the AI supposed (correctly) that it was pointless to fire on the 5 flyers because either they would be disposed, or that the risk of friendly fire by my XBowman was too great. Then the AI moved my crossbowman to a better position, toward the rearmost enemies.

I would like to know if it can be a bug or if its a behavior that can be expected. I dont remember seeing that before though.

Well thats not for a lost quarrel on a won battle, I think you can understand that. I rely on some items for my defence against some uber combattants, and if they dont works, bad things can happen to my units.