[Gameplay] Enemies moving through and then being stuck in place by Azir ult

I played a game of Azir earlier and had a bug occur two times during the game with his ultimate. You can watch the two instances of the bug here (and a cool play).

In the first clip, Aurelion Sol walks through the wall, and then appears to be stuck in place for a few moments before he is able to use his ult. In the second clip, I use my ult as Poppy is dashing towards me. She slides right through the wall, and the CC timer appears below her health bar. She's stuck in place with nothing around her until she dies.

I'm not entirely sure how to reproduce this unfortunately. After the play with Poppy happened, I assumed it had to do with a champion dashing as they are hit by the wall, but in the fight with Aurelion Sol he simply walked right through it while Sejuani got knocked back as she should. Perhaps it occurs when a champion is in a specific location when the wall is sliding along.