Flame Bolt issue on Green

[Dookky]

Greetings and Salutations,

I've noticed that flame bolt on Green seems to be dependent on z-axis position of me and the mob as to whether or not it works. IE, If I'm standing on a mountain and my pet is tanking a mob below me, if I cast flame bolt there is a high likely hood that it won't hit, no message indicates that it missed or was resisted, it just simply vanishes.

Is this an intended mechanic?