When a mob is pushed against a shulker box and the top of their hitbox is higher than the top of the shulker box, and the shulker box is then opened, they visually teleport to the top of the shulker box, and when the shulker box is closed they go back down.

How to reproduce

1. World download: World.zip
2. Open and close the shulker box

Observe the husks facing facing the south or east side of the shulker teleport up to the top of the shulker box when you open it. When you close it, they hang there for a second, and then teleport back down. The mobs still collide with any blocks above the shulker box.

Note

Because of the NoAI tag, the husks shouldn't able to fall down the shulker box after closing it. That would happen especially if their hitbox was inside the shulker.

The NoAI tag was used so that husks do not move away from the box, but this issue can be seen on regular survival playthrough as well.