[GAMEPLAY] Janna Ult Knockback Ignored

Although I cannot provide any evidence, this has happened twice. On occasion, Janna's ult will fail to knockback enemy champions. This has happened twice, but I can't remember the exact situation of the first time. It just happened in a game where I was in lane, trying to knock away a Braum. He was about 3/4 of the ult away from me before I casted it. He didn't have shield up because he had just used it (I'm not sure if that would even affect it.) He was running directly towards us. I ulted and he simply continued running towards us. I was exhausted at the time, and I had Braum's passive on me at 3 stacks.