[Gameplay] Azir ult not knocking back all targets

I played a game where my Azir ult worked as I expected it to except it never knocked back the enemy Blood Moon Thresh. I don't know if it properly applied damage to him, but I did see it knock back other enemies while leaving him in place. Link to the match history page, in case that's useful: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1727594317/44428905?tab=overview. I haven't attempted any reproductions, but it happened 2 or 3 times in that game, every time the ult would have hit him.