When teleporting a Y-Level of 0.00001 below the top of a block (For most blocks, at the Y-Level of an Integer + 0.99999), the player is unable to move or look around. Attempting to sprint or fly does nothing, although sprinting will create footstep particles and play the walking sound.

To reproduce, use the command /tp @p ~ ~-0.00001 ~

At a Y-Level of 0.00002 or more below a block, the player will fall through the block (which I believe is the intended behavior.