When standing over the edge of a block that has a door on top of it. Opening and closing the door changes the visual of a crouch. A closed door while standing on a ledge doesn't allow for the crouching pose to happen. When shift is still being pressed and the door opens, the crouching pose will still happen.

When recreating this in first person, the POV is from the crouch perspective. Even if the player doesn't seem to be crouching in third person. This is only resolved when the door is opened and the player stops crouching.

Link to video in google drive: Example video