[GAMEPLAY] Champion Stopping?

Frequently, when I'm playing the game, my champion will suddenly stop moving.

I am not pressing the 'S' key, nor have I reassigned that to another key. I am not pressing any key, for that matter.

I right-click somewhere for the champion to move, she moves about half way there, then stops.

This has interrupted numerous situations where I was chasing or being chased, in either case with bad results for me.

Please note, I am not talking about the annoying behavior of how if you are chasing someone and they run into a bush and disappear, you stop. I am also not talking about when they disappear into the 'fog of war' - out of your sight - and then your champion stops. This is something else. It's been happening since two or three patches ago. I have never noticed it before then.

Has anyone else noticed this happening?

Edit: This does not happen all the time. It seems random from my point of view. I cannot intentionally recreate this bug.