Bug: Yasuo vs Pantheon

Hey guys, so recently I've been trying to improve my skills with Yasuo so I pick him as often as possible, but the last couple of games I laned against a Pantheon and noticed a frequent bug. When the first game started, I was wondering if Panth's shield would be able to block Yasuo's Q, so I tried it as soon as I could, and sure enough it did. The problem is that the next time I used the Q against his shield, it actually dealt damage to him and didn't proc his passive. The game went on and the bug became way more annoying, since there were moments where I really needed to land my Q for the sake of using a combo or just applying poke, but still the shield would block it. The problem is not that he can block Yas's Q, I would be perfectly fine with it, what bothers me is that it seems to be completely random when the shield will block the Q or when it won't. For example, there was one particular moment in the game where I used Q on Panth and dealt damage to him even though he had the shield, at that point both of us were pretty low on health, and since the shield hadn't blocked my attack I decided to go in with E and use Q at the same time to get the kill....You can imagine how frustrating it was to see my Q not dealing damage and receiving a spear to the face in what would've been an easy kill... Some of you may think that the shield will block the Q one time and the next time it won't, but that's not the case since I noticed that there were times in which I would be able to hit him frequently despite his shield, and there were other times in which my Q would be completely useless and Panth would be able to deal a lot of free damage. I know many of you guys don't feel any love for Yasuo, but please support this thread so that Riot can fix the problem. TY for reading and sorry if I wrote too much :)