[GAMEPLAY] Braum's passive's bugged.

So here is the deal, it happened to me and a friend while we were duo bot, and I was playing Braum as 3 stacks were already applied to the opposing marksman, my friend which played Kalista at that time did the forth auto attack to proc Braum's passive but I guess due to the lack of vision in the bush he got in before the last auto hit him, he was not stunned nor did he take any additional damage and the stacks were rewinded, as if they weren't on the enemy at all, this scenario happened a few times in one game and some more the game after this one, so I'd want to know if it is intended or is it a bugged that hasn't been reported.