Were you taking casualities from towers?

Also javelins are shared in a sense. If the unit had a captain with it that would possibly add 6 javelins. That leaves 9 each to be thrown since the captain can't thow.

Also there is the animation to throw but they don't.

Occasionally I get units that have done over a dozen animations but no javelins were released or only a few. What quite often happens is they go through the animation the unit then moves out of range or they are forced to skirmish.