Player glitches inside of shulker box when opening on the floor under them

I first observed the issue in multiplayer 1.16.1 but it is the same in singleplayer. When placing a shulker box under my feet in a 3 block high room so my head is directly against the ceiling and open it, the player falls inside of the box and stays there. Upon closing the inventory and therefore the box closing the player returns to normal.

To reproduce, simply replicate the setup shown in the video clip below.