Kennen's E Get Toggled Off by Bumps (VIDEO)

I don't know if it's actually a bug, or just a weird interaction. When Kennen engages his E and then gets bumped, the E automatically gets toggled off (as if the player pressed E again). I've seen this bug/interaction many many times (I'm not entirely sure if it actually does it 100% of the time).

Steps to reproduce: -Play Kennen vs any kind of bump (Alistar, Yasuo, etc.) -Start the E -Get bumped -The E should get toggled off.