[GAMEPLAY] Blitz's Q not always working as intended?

Unfortunately I don't know how to duplicate this, but it definitely happened.

So I just played an Intermediate Bot game and went support Blitzcrank. I was laning against Zilean and Sivir Bot. At level 1 Sivir Bot had her Q, not her E and I also at level 1 landed a stun, which did not pull her. Immediately my ADC commented on it so it wasn't like it only happened on my end. It was at pretty long range and it honestly looked like Sivir Bot was still stunned for a short length of time, but was never pulled by my Q. Once again, she was level 1 and didn't have her spell shield so that was not what it was. It never happened again throughout the rest of the match however.

This makes me wonder if that bug they talked about with Sivir's Spell Shield blocking auto-attacks if she hit it in an exact frame was related to her spell shield at all. It seems to me like it's possible that Sivir is just somehow not feeling the full effect of things that hit her potentially at random. Also reminded me of the Xin Zhao bug everyone is having right now too where is Q isn't working correctly, as if there's a chance that any partial CC ability could just randomly not work as intended.