I have noticed 3 times now a bug that can occur with Blitzcrank involving being pulled, flashing away, and still being knocked up by his Power Fist Ability. Unfortunately, I do not have any video or screenshots of the bug, but will explain how it works, step-by-step.
1. Blitzcrank pulls you in with his Rocket Grab ability.
2. Your champion flashes away from Blitcrank putting an inch between you and him.
3. Blitzcrank activates his Power Fist ability and punches the air where you once stood.
4. You champion still gets knocked up even though you have already gotten away from him and he is not close enough to hit you with his Power Fist ability now.
I have explained the Bug/Glitch in full above, and hope that Riot could please look into this and fix the issue.
-Thank you for your time.