Jarvan IV Ultimate bug (New SR)

Played a casual draft game as Jarvan, I noticed that at one point in the game when I ulted the enemy Janna, she was trapped within the ult range, but casually walked through it right afterwards. I don't have a replay to show it, but I want to note that she had no cc immunity on her, and she did not use any abilities during that time either. Think this is just a bug developed from the transition to the new Summoner's Rift, anyone else have any experiences / thoughts on this?