SpellManager.Cast fails miserably with Holy Word :Chastise and Serenity

[Gilderoy]

So, I'm writing a Holy Priest CC (well an extention of UPaHCCBT)
SpellManager.Cast fails to cast both Holy Word: Chastise when you are in Serenity Chakra that Holy Word Serenity (also in Serenity Chakra ofc)
What's the problem?
Holy Priest have a Stance called Chakra, we are interesed in the stance Chakra: Serenity.
Holy priest have a Spell in theyr spellbook calle Holy Word: Chastise that if you are without Chakra con only be casted on enemy.
if you are in Chakra: Serenity the spell Holy Word: Chastise transform itself to became Holy Word: Serenity.
The spell remain the same on the SpellBook but on bars it will change in Holy Word: Serenity.
the problem is Holy Word: Serenity is one of the best heal of a holy prist.
SpellManager.Cast("Holy Word: Serenity") just return fail and do nothing
SpellManager.Cast("Holy Word: Chastise") return true but in wow give the error Invalid Target and no spell is casted
So what can we do?
thanks all for your help! ^__^

 

[Gilderoy]

Ok i found the solution by myself
SpellManager.Cast("Holy Word: Serenity") does not work
SpellManager.Cast(88684) does not work
SpellManager.Cast(WoWSpell.FromId(88684)) DOES WORK!
I'd be realy curios why.. realy..