[GAMEPLAY] Shaco's Jack in the Box's do not always go off for jungle monsters

I recently started playing Shaco fairly regularly as a jungle. Occasionally (I have had it happen against blue golem, the Gromp, and the dragon) the jack-in-the-boxes will not activate and will remain stealthed instead of attacking the jungle monsters. There seems to be no pattern to this behavior; I have had 3 boxes go off on a monster, and one remain stealthed.

I know it is not a range issue, as I place the boxes directly next to the monsters.

Similarly, some jack-in-the-boxes attract aggro from the monsters, allowing Shaco to utilize backstab. Others, for whatever reason, do not attract aggro after activation.

I have not been able to determine a source or pattern in this bug. Has anyone else had this issue?