Every so often when killing an enemy when Skeleton key spell, I will not receive an extra turn.
From what I can tell, it only ever happens when the spell doesn’t kill the first enemy but DOES kill the last enemy. That being said, the vast majority of the time, it does work normally, but I’ve lost a few games because of it.
EDIT: This is happening on PC/Steam. I have not tested it on mobile.
There might be something else involved here, could you please post the talents your hero is using? The level 100 assassination talent might play into this.