Poppy Stun Triggering Late, and Stuns for Way Longer than Intended

I was playing a game of ARAM a couple of minutes ago, and I was against a Poppy. The game progressed well past the half an hour mark, so every death mattered. Poppy built super tanky, and was just knocking me into the wall repeatedly, stunning me, as any good Poppy player should. After a stun or two, I noticed that the stun wasn't triggering on impact of the wall, but instead about a second after, while leaving me stunned for the extra second before triggering, making it about 3 seconds of stun duration. I might be incorrect, and just caught up in the moment, but I watched my ability icons light up after the charge, and then go grey for the stun after about a second. It's entirely possible that I was also just really caught up, but the Poppy player agreed that the stun seemed to go on longer than intended. If this is actually a bug, it should be addressed rather quickly, as it can really unbalance a fight really quickly. If it's just a graphical issue though, it should still be addressed, because thinking I can use my abilities and summoner spells even though I'm stunned is bound to cause a lot rage for a lot of players.