Piston glitches into shulker when pushing it into the world border.

When pushing a shulker using a piston next to the world border, the piston glitches into the shulker.

 How to reproduce

Start by summoning a shulker using the following command:

1. /summon shulker ~ ~ ~ {NoAI:1b}

1. Place a piston next to the shulker in an attempt to push the shulker outside the world border.
2. Place a block of redstone to activate the piston and observe.

Observations and Expectations

Observation: Piston seems to glitch inside the shulker when pushed next to the world border. 

Expectations: Piston shouldn't glitch inside the shulker even if its forbidden for the block/mob to exit the world border.

Notes: Discovered while testing MC-271320.
            Relates to MC-82010.