What I expected to happen was...:
That the shulker would not move.
What actually happened was...:
The shulker moves one block down and when you try to stand on it, you start to glitch out (shake up and down). Re-logging solves the issue.
Steps to Reproduce:
1. Place down a command block with this command:
/summon ArmorStand ~ ~1 ~ {Invisible:1,Passengers:[{id:"Shulker",NoAI:1,Invulnerable:1,CustomName:"test"}],NoGravity:1}
2. Activate the command block and fly atleast 80 blocks away, so that you can't see the shulker anymore.
3. Fly back and notice the shulker has dropped down one block.
Related issues
Attachments
Comments

Can confirm. It is only a visual glitch and only the Shulker entity itself needs to render not anymore, you do not have to get out of render distance.
Is the same for FalingSand, but seems not to happen for a Creeper.

NeunEinser it is not only a visual glitch. If you try to stand on top of the shulker you will start glitching up and down.
So, let's call it a client-server-desynchronization then 😃
Can confirm for 16w07a
Confirm for 1.9.3 pre-2 and I get this warning message in the Game Output [Client thread/WARN]: Received passengers for unknown entity

Please see if 16w32a fixed this issue.
Fixed for 16w32a (probably as a result of fix MC-96954)