Hack/Exploit/Major Bug: Tristana hops out of all Blitzcrank CC
So I just played a game where I was Blitzcrank and the enemy Trist was able to "leap" out of not only my pull, but also my knockup. She was actually leaping away from me while in the middle of the knockup. Midair. She also kept leaping in the middle of my blitz pulls to cancel them completely. She told me that she got out of my pulls by "timing" her jump, but she had no response when I later asked how she was cancelling my knockup as well. No, she didn't have cleanse or QSS, she was doing it from level 1.
If this is a hack/exploit, I have the persons username for Riot, as there is no option to report for "hack/exploit" on the post-game screen. If this is a bug, then it's gamebreaking and needs to be fixed immediately. You should not be able to leap out of stuns, pulls, and especially knockups.