Its probably because when the stun wears off - he LOSES you as a target. So just like with Reckoning he was "right-click targeting" you while chasing, putting those Thrash charges into you. But when he lost the target - all charges went away. Could you test with another person? Like Warrior with Taunt. You pull the Scorp & build the charges - then instead of stunning, the Warrior just taunts him off you. Will the charges disappear?
Its probably because when the stun wears off - he LOSES you as a target. So just like with Reckoning he was "right-click targeting" you while chasing, putting those Thrash charges into you. But when he lost the target - all charges went away.
Could you test with another person? Like Warrior with Taunt. You pull the Scorp & build the charges - then instead of stunning, the Warrior just taunts him off you. Will the charges disappear?