[Shaman] Clearcasting proc not consumed

[panplume]

The Clearcasting shaman proc coming from the Elemental Focus talent is not consumed by subsequent casts.

Howto reproduce:

1. spec into Elemental Focus (Elemental tree).
2. cast a spell until it crits (the Clearcasting proc is added to your buff list).
3. cast more spells (bug here, the Clearcasting proc is not consumed).

What should happen:

on step 3. the spell should have his mana cost reduced and 1 (one) charge of the Clearcasting buff should be consumed.

[Kentamentiu]

When I get clearcasting, on the first cast, the buff remains at 2 stacks and on the second cast both stacks disappear.

[panplume]

Going deeper into Elemental with Lightning Overload, I can see both behavior happening at random. Sometime the Clearcasting proc will not be consumed (disappear after its 10s duration), sometime it disappear after 2 more cast (without the counter on the buff being decreased, never showing "1" more stack available).