Entities are invisible when at or above the maximum build height (x, 127, z). Tested in creative mode with arrows, mobs, and thrown eggs. Shown is a pair of chickens in love mode being led up one block from y=126 with seeds, and the ignite button for a creeper located at y=127.
This issue is likely related to MCPE-6811, which is fixed as of 0.9.0.