[GAMEPLAY] Displacements from hooks and knocks sometimes fizzle

I've noticed that hooks (in either direction, e.g. Blitz or Amumu) and knocks (e.g. Blitz E) sometimes fail to actually displace anything. I don't know if it only happens when playing co-op or if it also happens in PvP, but several times now I have had these abilities function in everything but their displacement. Using Amumu's Q stuns the target, and then Amumu simply stands there without getting pulled to the target. Landing a Q with Blitz stuns the target, and then the target will simply stand there without getting pulled. Punching with Blitz E makes the target hop a few inches into the air for a fraction of a second and then keep right on walking.

These don't happen all the time, and I'm not sure whether it's related to the way the bots process or queue up their commands, but other players do see the same thing I'm seeing (i.e., it isn't just a client-side visual bug). I played Blitz on a low-level account earlier today and had a Q fail to move a Swain bot (lane partner saw it and was just as confused as I was), then later punched J4 bot with E and he basically ignored it as described above.

I apologize for not providing a consistent repro. All I know is that sometimes I use these abilities and the displacement does not happen. I have the .lrf from LoLReplay if that helps.