I was in my survival single player world, standing at my enderman farm in the End. I paused the game for about 20-30 minutes, and when I came back, my pause screen flashed briefly and then changed to the "You Died" respawn screen. The death message said I had fallen out of the world, despite the fact that my game was paused and I was in the middle of a platform. The game DID fully pause - all the enderman froze, no particles moved. Everything was fully paused and I somehow died. None of my items were there when I respawned, and I got back to the farm in under two minutes.