Failed Blitzcrank Pull

When I played a bot match just now, I was Blitzcrank, my friend was Pantheon, and we were bottom lane playing against an Ashe and Shen combo. When I activated my pull to get Ashe (She was standing just inside her turret range last-hitting) it stunned her for a second, but it did not pull her towards me. I have not been able to reproduce the glitch, and it may have been a one-time thing. We were too early in the game for any QS's or anything and it was Easy bots, so i know she didn't use a summoner spell to negate it. *Note: I was in Blitzcrank's classic skin if that helps.