Healing Hands not triggered by Echoes of the Charge (node from Shield Rush)

[Ark2]

I have 4 points in Cleric’s Hammer node of Healing Hands (100% triggered with a directly used melee attack and hit at least one enemy).
7-8 out of 10 times (not every single time) Healing Hands was not triggered by Echoes of the Charge (node from Shield Rush, which is a melee hit). I’m not sure if it is supposed to be triggered by Echoes of the Charge though.
Tested a lot but couldn’t figure out the reason.

Sometimes its echo did trigger Healing Hands, and sometimes it even triggered more than 1 Healing Hands (only 1 echo hit).
But according to node description of Cleric’s Hammer:

When you directly use a melee attack and hit at least one enemy, you have a chance to cast Healing Hands around the target.

So I suppose no matter how many enemies you hit with a melee attack, only 1 Healing Hands can only be cast.

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So,

1. Why most of the time Echoes of the Charge (node from Shield Rush) cannot trigger Healing Hands?
2. Why does Shield Rush or Echoes of the Charge can trigger multiple Healing Hands at a time (1 melee hit).

[Ark2]

Also, I forgot one thing.
1 Shield Rush should hit up to 3 times:
a. character colliding enemies;
b. final hit;
c: final hit echo;
Based on my tests, if a) triggers Healing Hands on a target, b) will not trigger again on the same target.
But if a) does not happen (character does not collide but final hit area of effect covers the target), b) can trigger Healing Hands.