What is your spark level ?
I think it works when the base spark skill reaches 360° angle (level 7 spark).Otherwise it may give negative angle andhave a weird effect.
I was playing at spark level 3.
In that’s case, I’ll increase it to level 7 and see how it goes.
When I set the level to 7 or higher, the angle of the fireball narrowed as description. Thanks for your advice!