Jinx Passive

I've had a couple of days recently of ARAM and the odd occasion I got , her passive didn't always trigger with every; assist, turret, inhib or kill. My friend is now playing a 5v5 Summoner's Rift as Jinx in bot lane and he got an assist on a kill and she didn't get her passive boost. We were wondering if it was just an occasional passive and it is now producing a cool down? Or that it was a bug, so we decided to report it anyway.

#Thanks for reading this and hopefully it's resolved soon.