[GAMEPLAY] Blue buff dealing damage without doing animation

I was on the practice tool trying Master Yi when I realized the blue buff wasn't attacking me but still was dealing damage. It just happened once so I don't know how to reproduce it nor how often this happens.

I know the video is pretty bad, so I'm sorry. I had the video on Plays.tv but it disappeared so that's the only thing I have.

Oh and it was on EUNE if this helps.