Stuck on a ''rock''

It happened that my champion gets stuck and can't move when passing by a specific rock in mid lane. This bug does not happen every time, but it has occurred at least 5 times to me during a game, getting me killed. :(

• This is the rock I am talking about - (RED ARROW)

http://s8.postimg.org/71my733yt/Warding_at_midlane_league_of_legends.jpg

(Sorry I couldn't make an IG video of it)