Yes, I did, and if I'm not mistaken, that issue is about how multiple simultaneous key presses don't register. I don't see how it's the same issue. (I hope I'm not coming across as argumentative, I'm legitimately confused)
I fail to see how this is a duplicate, as the issue only happens in Minecraft. If you could elaborate, that would be helpful.
I ended up solving the issue anyways; it was a software issue (which is strange nonetheless as it only happened when online). I have a soundboard program, and I think that the specific way it reads keyboard inputs somehow interfered with how Minecraft reads inputs.