Azir Ult Bug, Enemy Champs Walk Freely Through His Wall

I discovered a bug with Azir ult after 4.19 patch. I don't have a recording of the bug, but it happened so often that it shouldn't be hard to replicate. Sometimes, if an enemy champion casts an ability while you ult, it completely negates your ult. The animation still happens but the enemy champ can walk freely through your ult wall, or the wall will not hit them at all. For example this happened to me while a Cho'Gath casted rupture and I ulted. My ult went off while I got hit simultaneously with rupture, but my ult had no effect. The Cho then walked right through my ult and feasted me. It occurred again in the last game I played, when an enemy Quinn ulted at the same time I did. She walked right through the wall and then hit me with her abilities. There seems to be a correlation with casting ult the same time an enemy champ casts an ability, negating it.