Twitch ARAM passive is not activating Dark Harvest

Several times in my ARAM game as Twitch, I would shoot an enemy, my passive would stack on 2+ people, my Auto would activate Dark Harvest, we would kill the individual, and someone would escape with 2+ stacks, and 100 HP, Dark Harvest comes back off CD, and does not re-activate. Dark Harvest, Cheap Shot, Eyeball, Ult Hunter, Overgrowth, Demolish, / . Started noticing it after Stormrazor was purchased.

How to re-create issue: Load an ARAM as Twitch, play as normal, get passive on multiple targets, kill one before passive runs out (6 seconds).

Expected result: Dark Harvest activates off of Twitch passive True Damage poison after primary target dies and the 1.5 second CD happens.

Help me Rito! You are my only hope for my Rat Baby <3