Jinx Ultimate Glitch

I main Jinx, and that being said I play her a lot. The bug I'm about to talk about has occurred twice. It's simple:

Encounter 1) I fired Jinx's ultimate down mid lane, had vision the entire time, and it went directly through the middle of the enemy Fiora, dealing no damage. I questioned her in the all-chat, and she confirmed that, yes, it went through her somehow.

Encounter 2) (Different game, few days later) Again, mid lane, I launched Super Mega Death-Rocket up at the enemy Xin in hopes of a kill, but it didn't kill him. I didn't actually see this, but a few seconds later the ally Karma tells me that it went straight through him, and my friend whom I was skyping confirmed that he saw that too.

So in conclusion, Super Mega Death-Rocket seems to have a small chance of phasing right through enemy champions. Not sure what causes it, but I would assume this bug must have been added in version 4.18 or 4.17, as the second occurrence was just today, the last game I played, to be specific. The first occurrence I described was somewhere within the last 14 days, probably not so close to the 14 day mark, but I'm not sure when this took place exactly.