Rare Champion Interaction bug: Jarvan sometimes ignores the root from Soraka's E.
I guess the reason this has not been found for so long is that Soraka vs J4 lanes are rare. Well, not when you are a Raka top OTP in Diamond.
So my guess is that it has something to do with his shield, but not sure. The visual and audio effects of the root still show, but J4 can walk just like it was not there. Definetly weird.
I play a lot of toplane games, and so far this has happened ONLY when playing against Jarvan. Someone should look into this, it is quite annoying to die and lose your lane because of weird spaghetti code on old champions.