Xperia Z5

Mobs, animals, bosses, flying objects (arrows, fire balls, wither heads) and anything else that is not a block or half a block disappears if it reaches a specific distance (I guess four chunks?), This causes anything to disappear and pause until you get close to it, it's also related to the beacon beam problem, because the beacon itself disappears after it exceeds the entity rendering distance.
Even the wither boss disappears, causing the sky to go back to normal instead of staying in the wither sky mode.

How to produce:

Create the T shape of soul sand.
Put three wither skeleton skulls on the top.
Fly far away.

Youll notice that the sky will go normal, the health bar of the wither will disappear. If you go back to it, you'll see that it's still spinning as if it was paused.
So this bug been there for a long time and got worse after 0.17.0.