When trying to fire beyond the weapon range, merc often says "bad chance to hit" quote and refuses to fire (you have to click again to fire).
It's very annoying in NCTH, because weapon's range is not a big problen in this system - you can fire at 1.5x normal weapon range and hit.

Another problem is that AI uses the same routine to determine chances to fire or taking cover.

INT8 ChanceToGetThrough( SOLDIERTYPE * pFirer, FLOAT dEndX, FLOAT dEndY, FLOAT dEndZ )

And if this function does not work correctly (in NCTH), maybe it can also cause the known "AI refuses to fire" problem?