Are spell-shields not working?

I was playing an ARAM as Gangplank and the enemy team had a Sivir. Several times during the match I q'd her and she shielded properly, but she took damage. I wasn't paying close enough attention to see if she was also getting the mana back or not. It wasn't a flaw on my screen, she noticed it happening as well.

Then, earlier today, I was playing Nocturne (Nemesis Draft) against a Garen top lane. While my shield worked properly when I blocked his ult or a TF stun card, it did not work on his Q. I did block the silence, but not the damage.

Is this intentional or not? I know Sivir should be able to shield Gangplank's Q.