Double attack threshold (Path of Radiance)

//ads -- adsterra.com -- native banner
?>
As commonplace in Fire Emblem Games, a unit in Path of Radiance attacks twice if the difference between its speed and the enemy's speed reaches a threshold. Fire Emblem Wiki states that this threshold is 4.
In Chapter 15, I have the following Marcia (speed = 22)
trying to attack Muarim (speed = 18).
Even though she reached the threshold (4), she won't attack twice. Why?
Pictures about "Double attack threshold (Path of Radiance)"



How much speed do you need to double in Fire Emblem?
In most games up to Fire Emblem: New Mystery of the Emblem, double attacks occur when the attacker has an attack speed of at least 4 more than his opponent.Why do some units attack twice Fire Emblem?
Attack speed indicates which units get to attack twice in a single turn. This can easily be seen by preparing the attack command against enemies. Another way to check is by checking the stats of your character and the enemy. If your attack speed is greater than 4 against the enemy, you get to attack twice.What is fe3h speed?
SPEED (SPD) = The speed stat affects a unit's avoidance rate. It also allows a unit to strike twice if the speed stat has five more than the opponent.Fire Emblem: Path of Radiance -- Decisive Attack
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Vova Krasilnikov, Somchai Kongkamsri, Anete Lusina, Anna Shvets