This happens sometimes in 1.4.3, the ranged units just don't fire on enemies right in front of them. Sometime pressing f4-f4 will wake them up, but sometimes not, or it's too late because a unit(my time) has been destroyed by bad programming. I hate re-loading the game because it start to make it lag but I have to because it's so much more time wasted if a unit dies.
There's not much else to say, make them always shoot enemies in range, always.
If anything gets changed about how they function please have devs post in detail about it.
