Fire arrows bug?

[Sir Nicholas Altman]

In Fots I tried to burn towers and gates with fire arrows. But every time I set my archers to fire fire arrows on towers they string the bow cord and are about to fire but then they give up and stop firing and they just stand there. They don't fire on anything. Then I tried few custom battles and always the same. I tried with Shogun 2 units and the same thing happened. They just can't fire on wooden buildings the fire arrows.

[Lokgar]

Yeah for some reason targetting buildings wtih fire arrows cancels the spell effect so they don't use them thus they can't actually shoot at buildings! Super frustrating!