Why would my archers ignore "Fire Closest" orders?

[K]

If archers aren't in range, they will run up until they are in range and then fire.

But, if a particular unit it in melee, it usually won't fire.

If sounds like your fast maiden ran into melee with the fast barbs just trying to get into range.

Shortbows generally want to be in the middle of your battle setup, or a little back from the middle depending on the firing orders. Only longbows can fire from the far back.