For some reason the Wither disappears when he is a short distance from the player and then reappears again when he is closer. When this happens the sky goes from dark to normal in a short amount of time as if the Wither is really far away from the player. This didn't happen in previous versions of mcpe. My render distance is at max.

Steps to Reproduce

• Create Flat (Creative world)
• Summon Wither.
• When the Wither is a short distance away from you, he will disappear and then reappear again when he gets close enough to you.