Blitz Q won't pull through terrain

The Q grabbed and pulled Alistar, but he stopped at the wall near double golems. It happened twice in one bot match. I tried to reproduce it on a custom but couldn't. I don't think he ulted because there was no roar, but I doubt his ult cancels displacement anyway.

I wonder if this is related to the shunting of units who would end up in the middle of a wall. It's possible a thin wall could cause shunting with Blitz since the grabbed unit is supposed to land in front of him.