Shulker Box Spawning Randomly

The Shulker Boxes keep spawning randomly in windows, under fence gates, on clay walls, and even under stairs that are attached to walls.

Special note: I don't have any mods on plus this happens even when I have the default resource pack on.

(I have a video of it too: https://www.youtube.com/watch?v=ZzvrMHG5Qdc&feature=youtu.be )