When a Shulker has an orientation set by the AttachFace nbt tag, setting the Shulker's NoAI to 1, the tag is ignored and the shulker snaps to the bottom block by default.

Steps to reproduce:

• Place a shulker down using a spawn egg on top of a solid block
• Place a dirt block on the north face of the shulker
• Run the command

  entitydata @e[type=Shulker,c=1] {AttachFace:2b}

  this causes the shulker to grip onto the dirt block

• Run the command

  entitydata @e[type=Shulker,c=1] {NoAI:1b}

  this causes the Shulker to orient to the floor block, ignoring the AttachFace tag.