Sivirs E (Spell Shield) not working properly. [GAMEPLAY]

So, I've played Sivir for some time now, and few times this happened: I was playing,everything's fine until I got into fight with Yasuo.. He got his third stack on Q, and used his tornado on me. I used my E (Spell Shield). It triggered the shield, gave me mana, blocked the damage but the tornado still knocked me up and Yasuo ulted me = lost a fight. I tried it after and it doesnt happen every time but it happens once in a while. Unfortunatly I do not have screenshot or video. Hope I helped. Looking forward to seeing You fix it :P . Cheers . Lenole - NA