Wearing the elytra and using it for a while provides a glitch mode where you can phase through blocks that are 2 tall (blocks that are in chest level of the player with a air block underneath) regardless of being a full block or transparent and regardless of wearing a chest plate on. This bug combined with the levitation effect of the shulker can be deadly as the fall damage you take without even being in high altitude can kill you if theres a block above you (End city ceiling).  this bug makes the player stuck within the block and cant move vertically up out of it even after breaking the block and though the player is not raised in altitude, it inflicts fall damage as if the player has fallen from a high height though in reality its been 4 blocks.