[GAMEPLAY] Poacher's Dirk - stacking bug

So.. I like to use Poacher's Dirk on smurf. I know i can't stack 2 (or more) in the same time, but when I saw that I need only 1 more stack I decide to buy another one so I can start stacking it after 1st one. And here's problem. After killing enemy blue i got my 1st Serrated Dirk and my 2nd Poacher show that i need 4 stack on it (so it was ok), but after killing gromp it still had that 4 on it. After killing wolves it didn't change as well and still had 4...

Not sure if it was only visual bug or Poacher did't get any stack - game ended like 20 sec after this.